2021

The incredible resistance of tardigrades to environmental stresses

Despite their life expectancy of 1 to 3 years, tardigrades are aquatic micro-animals remarkable for their ability to survive for very long periods of time under stress conditions as diverse and lethal as extreme temperatures and pressures, desiccation or even irradiation. The molecular mechanisms that confer this unique resistance to extreme conditions have remained unknown until now, despite centuries-old fascination with tardigrades.
Researchers in the Protein Dynamics and Flexibility by NMR group have combined nuclear magnetic resonance, atomic force microscopy, and light and x-ray diffraction techniques to characterize the conformational and physical behaviour of an intrinsically disordered protein, unique to tardigrades, which plays an essential role in this environmental stress response. They were able to determine at the atomic scale that this protein has highly flexible disordered arms surrounding a long central helical domain whose behaviour is highly temperature dependent. This protein, which is highly flexible and dynamic under ambient conditions, transforms under stress conditions to form fibres, which in turn form a hydrogel. The researchers were able to sequester other proteins inside this gel formed by the tardigrade protein and showed that they retained their conformational behaviour. The exact mechanism by which the formation of such gels protects the organism is still unknown, but it is possible that the formation of such an intracellular matrix allows the maintenance of biomolecules in their functional state. This transformation of the cell environment, which is perfectly reversible when the stress is removed, provides a better understanding of the unique ability of tardigrades to survive conditions that would otherwise be fatal to life.

Intrinsically Disordered Tardigrade Proteins Self-Assemble into Fibrous Gels in Response to Environmental Stress. Malki A, Teulon JM, Camacho-Zarco AR, Chen SW, Adamski W, Maurin D, Salvi N, Pellequer JL, Blackledge M. Angewandte Chemie International Edition 2021 ;61(1):e202109961

Contact : Martin Blackledge (Protein Dynamics and Flexibility by NMR Group)

A new technique combining single molecule FRET, NMR and SAXS to describe intrinsically disordered proteins

Intrinsically disordered proteins (IDPs), i.e. proteins without stable three-dimensional structure, are extremely dynamic and it is precisely this dynamics that allows them to function and bind to different interaction partners very easily and efficiently. Rather than describing IDPs with a single structure, ensembles of many conformers have to be calculated to adequately represent their conformational landscape. In the past, nuclear magnetic resonance (NMR) spectroscopy and small angle X-ray scattering (SAXS) have been used to provide experimental input for the calculation of such ensembles. A precise description of specific long-range distances has, however, so-far been missing.
IBS/FDP researchers (Naudi-Fabra et al.) have now combined single molecule fluorescence spectroscopy, Förster resonance energy transfer (FRET) in particular, providing precise distances up to 10 nanometers, with NMR spectroscopy and SAXS in order to determine conformational ensembles in agreement with all those experimental data. The authors could show that their calculated ensembles were of predictive nature and reproduced independent data that were not included in the calculation of the model. This multidisciplinary approach thus opens up new possibilities for the quantitative description of intrinsically disordered proteins.

Quantitative description of Intrinsically Disordered Proteins using single molecule FRET, NMR and SAXS. Naudi-Fabra S, Tengo M, Jensen MR, Blackledge M, Milles S. J Am Chem Soc In Press (2021) https://doi.org/10.1021/jacs.1c06264

Contact : Sigrid Milles (Protein Dynamics and Flexibility by NMR Group)

An exclusive licence on a patented vaccine technology developed at IBS

The ’Adenovirus’ team led by Pascal Fender in the Methods & Electron Microscopy group at IBS is working on the adenovirus proteins involved in the entry of this virus, which infects many animal species and humans. This team discovered a non-infectious virus-like protein particle mimicking this virus : ADDomerTM. In 2016, in collaboration with the EMBL in Grenoble, the researchers modified this particle to expose epitopes of emerging viruses, leading to the creation of a new vaccine platform. After filing a CNRS/EMBL patent in 2017, the results were published in Science Advances in 2019 (Vragniau et al., 2019). In 2021, the British company Imophoron has just bought a licence for this patent and completed a 4.7M€ fundraising to perform preclinical studies and to test vaccines against three viruses : respiratory syncytial virus, chikungunya, and SARS-Cov2. It will validate the ADDomer as a platform for future vaccines development.

Contact : Pascal Fender (IBS/Methods & Electron Microscopy group)

Andrea Dessen recipient of the CNRS silver medal

Andrea Dessen, team leader of the Bacterial Pathogenesis group, has been awarded the 2021 Silver Medal of the CNRS. This medal is presented to a researcher for the originality, quality, and importance of their work, which is recognized at national and international levels.

Andrea Dessen is graduated with a degree in Chemical Engineering from the University of Rio de Janeiro. She did her PhD work at New York University and her postdoctoral training both at the Albert Einstein College of Medicine (New York) and at Harvard Medical School (Boston), the latter with Pr. Don C. Wiley. She then worked as a staff crystallographer at Genetics Institute/Pfizer in Cambridge, MA, in the Small Molecule Drug Development Dept. Upon moving to France, she was hired by the CNRS in 2000 in Dr. Otto Dideberg’s laboratory at the IBS. As a CNRS Research Director she has been the head of the Bacterial Pathogenesis group at the IBS since 2012. In addition, she also directs a 2nd group at the Brazilian Biosciences National Laboratory (LNBio/CNPEM) in Campinas, São Paulo, thanks to a Laboratoire International Associé (LIA) partnership between the CNRS and the CNPEM in Brazil.

The main interest of both groups involves the structural and functional characterization of bacterial virulence factors and cell wall biosynthesis machineries, as well as the identification of novel antibacterial compounds in natural product libraries. The main techniques employed by the teams include X-ray crystallography, electron microscopy, high throughput screening and natural product characterization, as well as biochemical, biophysical and microbiological approaches.

Hélène Malet, winner of the CNRS Bronze Medal

Hélène Malet, Associate Professor at the University of Grenoble Alpes and researcher in the Electron Microscopy and Methods group of the IBS, has been awarded the CNRS Bronze Medal for the year 2021 for her work on viral proteins involved in viral replication and transcription (details). This medal rewards the first work of a researcher, which makes him/her a talented specialist in his/her field.

Viral replication and transcription are key steps of the viral cycle. Hélène Malet analyses the structure of viral proteins involved in these processes, in particular viral polymerases. During her thesis, carried out under the supervision of Dr. Bruno Canard at the AFMB, Marseille, she characterized by X-ray crystallography a polymerase structure of the Flaviviridae family, to which the Dengue virus belongs. Then, eager to learn a complementary method of structural biology, she did a post-doctorate in electron microscopy in the laboratory of Pr Helen Saibil at Birkbeck College, London. Since then, she combines her interest in electron microscopy and viral replication. She undertook a post-doctoral fellowship on the structural analysis of Peribunyaviridae polymerase in the group of Dr. Stephen Cusack at EMBL Grenoble, before being recruited as an UGA Associate Professor at IBS in the team of Dr. Guy Schoehn in the Electron Microscopy and Methods group.

Her research project focuses on the structural and functional analysis of bunyavirus replication, a viral order consisting of many highly pathogenic human viruses against which no drugs or vaccines are available. The latest advances in electron microscopy and the presence of state-of-the-art electron microscopes at IBS and ESRF enable to determine high-resolution structures of these essential enzymes thereby revealing their modes of action, a key step for the future development of anti-virals. In the longer term, this project aims to understand the mechanisms of interactions between viral proteins and host proteins involved in the regulation of viral replication, combining high-resolution electron microscopy of isolated particles and cellular electron microscopy, allowing an integrative view of these processes. This project is financially supported by the ANR (HiPathBunya) and the Institut Universitaire de France. It will make an extensive use of IBS technology platforms managed by ISBG and funded by FRISBI and Gral.

Click and Collect at High Resolution : a new strategy to unravel the secrets of bacterial division

Bacteria adopt a morphology that is adapted to the selective pressure of their environment, which makes it an essential feature for their survival. This shape is intimately linked to the synthesis of the bacterial cell wall. In Gram + bacteria, such as Streptococcus pneumoniae, the cell wall is mainly composed of a thick layer of peptidoglycan (PG), which forms a three-dimensional network of sugars and peptides at the surface of the cell. Although the PG synthesis machineries, called divisome and elongasome, have been identified for decades, their dynamics of assembly and remodeling of the bacterial cell wall in time and space remain enigmatic. In order to study these processes at the nanometer scale, researchers of the PG group in collaboration with the PIXEL team of IBS (D. Bourgeois), a chemist from the DPM (Y-S. Wong) of Grenoble and the B3P team of the MMSB in Lyon (C. Grangeasse), have developed a labeling technique for newly synthesized PG using bio-orthogonal chemistry (click chemistry) coupled with high resolution fluorescence imaging (dSTORM), and in silico modeling. This pioneering work describes the dynamics of PG synthesis in the pneumococcus with previously inaccessible details. In the future, this approach could be used to elucidate the mode of action of new antibiotics, and could also be adapted to the study of cellular processes in all fields of life.

Nanoscale dynamics of peptidoglycan assembly during the cell cycle of Streptococcus pneumoniae. Trouve J, Zapun A, Arthaud C, Durmort C, Di Guilmi AM, Söderström B, Pelletier A, Grangeasse C, Bourgeois D, Wong YS, Morlot C. Current Biology 2021 ; S0960-9822(21)00576-5

Contact : Cécile Morlot, (IBS/Pneumococcus Group)

Zooming into the chromophore environment of a fluorescent protein with solution NMR spectroscopy

Fluorescent proteins of the GFP family that change their fluorescent state upon illumination at specific wavelengths are widely used markers for super-resolution imaging modalities. The photophysical properties of these proteins, however, crucially depend on the environmental conditions in which they are expressed and used. Currently, strategies based on rational design to improve fluorescent proteins mainly exploit the mechanistic information available from X-ray crystallographic structures that lack important information on conformational dynamics, protonation states, and hydrogen-bonding, as well as their dependence on physicochemical conditions. In this collaborative work involving the NMR and I2SR groups, we focused on rsFolder, a reversibly switchable green fluorescent protein that has been designed at IBS. We demonstrated that solution NMR spectroscopy can detect subtle changes in the chromophore environment with atomic resolution, providing new insights into the pH-dependence of the observed photo-switching properties of rsFolder. Our results can be exploited to design and test new FP variants with higher robustness towards environmental changes. This work also introduces NMR spectroscopy into the field of fluorescent protein research as a new tool to probe chromophore state populations and dynamics as a function of a variety of environmental conditions.

Disentangling chromophore states in a reversibly switchable green fluorescent protein : mechanistic insights from NMR spectroscopy. Christou NE, Giandoreggio-Barranco K, Ayala I, Adam V, Bourgeois D, Brutscher B. Journal of the American Chemical Society 2021, 143, 19, 7521–7530

Contact : Bernhard Brutscher (IBS/Biomolecular NMR Spectroscopy Group)

SARS-CoV-2 spike protein interactions with model lipid bilayer membranes

Image courtesy of the ILL

The SARS-CoV-2 spike protein is know to bind with ACE2 receptors on cell surfaces (especially in the lungs) thus allowing the entry of the virus into human cells. Scientists from the Institut Laue-Langevin (ILL), in collaboration with the Institut de Biologie Structurale (IBS), the Paul Scherrer Institut (PSI) and the Australian Nuclear Science and Technology Organisation (ANSTO), focused on the interactions between the spike protein and the rest of the cell membrane. Several model cell membranes were created using supported lipid bilayers (SLBs), varying from single layers to more complex membrane structures. IBS successfully manufactured a stable SARS-CoV-2 spike protein (sSpike), containing the soluble part of the protein and the receptor-binding domain. This sSpike was then introduced so that interactions could be observed within the varying complexities of synthetic and natural membranes. The membranes were then studied at the ILL using neutron reflectometry, which permits sub-nanometer levels of resolution. Reserchers saw a degradation of the lipid bilayer as soon as sSpike was introduced (with and without the presence of sACE2). sSpike is able to significantly strip away lipids from the cell membrane, disrupting and potentially entering directly through the cell membrane. These fundamental research results, published in Scientific reports, could pave the way for further investigations and potential development of more effective therapeutics or future vaccines.

Lipid bilayer degradation induced by SARS-CoV-2 spike protein as revealed by neutron reflectometry. Luchini A, Micciulla S, Corucci G, Chaithanya Batchu K, Santamaria A, Laux V, Darwish T, Russell RA, Thepaut M, Bally I, Fieschi F, Fragneto G. Scientific Reports 11, 14867 (2021)

Contact : Franck Fieschi, UGA professor attached to the IBS (Membrane & Pathogens group)

A bacterial toxin guided by a human protein

Pseudomonas aeruginosa can cause nosocomial infections via the ExoU toxin, which acts on plasma membrane lipids, causing their rupture and necrosis in the host cell. By discovering that ExoU requires the host DNAJC5 protein for its necrotic activity, IRIG researchers have identified the Achilles heel of this toxin.
Pseudomonas aeruginosa is an opportunistic pathogenic bacterium causing nosocomial acute infections, as well as fatal chronic infections in cystic fibrosis patients. Clinical isolates are frequently multi-resistant to antibiotics, which complicates the management of infected patients. P. aeruginosa possesses an arsenal of virulence factors, the most active of which is an injectisome that injects toxins directly into target cells. ExoU is the most harmful toxin injected by this system. Its necrotizing action is linked to its phospholipase activity (Figure) that causes the rupture of the plasma membrane of the host cell, and results in severe lesions in infected tissues.

To carry out their biological activity, bacterial toxins often hijack molecules or mechanisms of the host cell. IRIG researchers used a genetic screen employing CRISPR-Cas9 technology to search for genes that might be involved in ExoU toxicity. Only one such gene was identified ! This gene encodes the human DNAJC5 protein, which is known to play a central role in the secretion of some cytoplasmic proteins via an unconventional vesicular transport system (MAPS). The researchers demonstrated that DNAJC5 guides the toxin to the plasma membrane of the host cell, where ExoU can exert its toxic activity (Figure). They showed that cells deficient in DNAJC5, or Drosophila in which the DNAJC5 gene orthologue was down regulated, are largely resistant to ExoU toxicity.

The transportation system provided by the DNAJC5 protein is thus the Achilles heel of Pseudomonas aeruginosa’s ExoU toxin. This discovery could be used to prevent the devastating action of ExoU in acute P. aeruginosa infections. .

The bacterial toxin ExoU requires a host trafficking chaperone for transportation and to induce necrosis. Deruelle V, Bouillot S, Job V, Taillebourg E, Fauvarque MO, Attrée A and Huber P. Nature Communications, 2021

Radical-based chemistry for the assembly of the [FeFe]-hydrogenase active site

[FeFe] hydrogenases are metalloenzymes capable of catalyzing the reversible oxidation of molecular hydrogen. They use a unique organometallic center called H-aggregate, consisting of a [Fe4S4] center linked to a binuclear iron center [2Fe]H. The latter corresponds to the hydrogen binding and conversion site. The physicochemical and structural properties of this center serve as a source of inspiration for the development of catalysts for the wider use of molecular hydrogen as a renewable energy source. IRIG researchers are unveiling the mechanisms of production and assembly of this metal center, which involve a complex radical chemistry .

The biosynthesis of [2Fe]H requires the coordinated action of at least three accessory metalloproteins HydF, HydE and HydG. HydG is responsible, from L-tyrosine, for the production of the ligands cyanide and carbon monoxide, in the form of an organometallic complex termed complex-B. The latter serves in turn as a substrate for HydE whose reaction and product remain unknown. HydF serves as a scaffold on which the [2Fe]H center is built before being inserted into the hydrogenase. Researchers from Irig are studying the catalytic mechanisms of transition metal containing metalloenzymes, but also the mechanisms of synthesis and insertion of these metal sites into the enzymes in which they are to be inserted. In collaboration with UCDavis and the University of Illinois, they published the complex-B bound HydE crystal structure, revealing for the first time both its unique (3-cysteinate)Fe(CN)(CO)2 configuration and its binding mode. Furthermore, by triggering the reaction, either directly in the crystals or just before crystallization, they were able to observe a new mononuclear pentavalent iron species, probably related to the product of HydE. Analysis of the conformational changes observed in the different structures suggests a directional movement for substrate access to the active site and product evacuation, allowing them to be protected from possible hydrolysis upon contact with the solvent. This work raises new questions about the complete mechanism of the enzyme which acts as a nano assembly line.

Crystal Structure of the [FeFe]-Hydrogenase Maturase HydE Bound to Complex-B. Rohac R, Martin L, Liu L, Basu D, Tao L, Britt RD, Rauchfuss TB, and Nicolet Y. Journal of the American Chemical Society, 2021

Contact : Yvain Nicolet (IBS/Metalloproteins Group)

SARS-CoV-2 : a new mode of transmission

Broadly speaking, cells have receptors on their surface, some of which are used only for virus attachment, while others can contribute to the cellular barrier crossing. The S-glycoprotein, located on the surface of the SARS-CoV-2 Coronavirus, allows the entry of the virus into human cells via its interaction with a receptor, the ACE2 enzyme, on the surface of infected cells.
IBS Scientists (M&P group), in collaboration with the CAID group and the IBS electron microscopy platform, as well as Spanish and Italian researchers, have demonstrated that lectin receptors (DC-SIGN, L-SIGN , MGL and Langerin) of immune cells are also able to recognize the S protein of SARS-CoV-2. This interaction involves a multi-site recognition of the S protein by exploiting the different surface glycans (sugars) of the S protein. It does not cause direct infection of cells by SARS-CoV-2 but DC-SIGN and L-SIGN are able, once they have attached the virus to the cell, to transmit it to permissive cells possessing ACE2. The S-glycoprotein thus appears to possess a whole set of keys to allow SARS-CoV-2 to proliferate.
These results, already demonstrated on pseudo viruses a few months ago in pre-publication, are now confirmed by the use of authentic SARS-CoV-2 viruses and on human respiratory cells. The researchers have also demonstrated that it is possible to inhibit this mode of transmission by using glycomimetics, molecules that can mimic the surface sugars of the virus. These glycomimetic inhibitors developed at IBS will constitute a first tool to study the relative importance of this mode of transmission. UGA press release

DC/L-SIGN recognition of spike glycoprotein promotes SARS-CoV-2 trans-infection and can be inhibited by a glycomimetic antagonist. M. Thépaut, J. Luczkowiak, C. Vivès, N. Labiod, I. Bally, F. Lasala, Y. Grimoire, D. Fenel, S. Sattin, N. Thielens, G. Schoehn, A. Bernardi, R. Delgado, F. Fieschi. Plos Pathogens ; 17(5):e1009576.
doi : 10.1371/journal.ppat.1009576.

Contact : Franck Fieschi, UGA professor attached to the IBS (Membrane & Pathogens group)

Molecular insights into the bacterial cell wall elongation process

The peptidoglycan (PG) is an essential component of the bacterial cell wall, and plays a key role in shape maintenance and cell division. Due to the importance of PG for bacterial survival, its biosynthetic machinery has been a preferential target for antibiotic development for decades. However, little is known regarding how cell wall elongation is regulated. In this work we show that the scaffolding protein MreC from the human pathogen Pseudomonas aeruginosa plays a key role in regulation of cell wall elongation through its ability to self-associate and bind to different protein partners, including Penicillin-Binding Proteins (PBPs), the targets of beta-lactam antibiotics. These results were obtained in partnership with the Laboratório Nacional de Biociências in Campinas and using data collected at the Brazilian synchrotron LNLS and at the Glacios cryo-electron microscope at the IBS, pave the way for a detailed understanding of how bacteria form their cell wall as well as for the development of new antibacterial agents.

Self-association of MreC as a regulatory signal in bacterial cell wall elongation. Alexandre Martins, Carlos Contreras-Martel*, Manon Janet-Maitre, Mayara M. Miyachiro, Leandro F. Estrozi, Daniel Maragno Trindade, Caique C. Malospirito, Fernanda Rodrigues-Costa, Lionel Imbert, Viviana Job, Guy Schoehn, Ina Attrée, Andrea Dessen. Nature Communication ;2987

Contact : Andrea Dessen (IBS/Bacterial Pathogenesis Group)

A new HIV-1 gp41 conformation as a target for broadly neutralizing antibodies

The HIV-1 envelope glycoprotein (Env) is the key target of neutralizing antibodies, blocking virus entry. Env is a metastable trimer composed of the receptor binding domain gp120 and the fusion protein subunit gp41. Upon cellular receptor binding Env undergoes a series of conformational changes notably within gp41, which pulls viral and cellular membranes into close proximity to catalyze membrane fusion and initiate infection.
In this article, the EBEV group and collaborators from the University of the Basque Country, the University of Zurich and the University of Lorraine present the crystal structure of gp41 locked in a fusion intermediate state. This structure illustrates the conformational plasticity of the six membrane anchors arranged asymmetrically with the fusion peptides (FP) and the transmembrane regions (TMR) pointing into different directions permitting a close apposition of viral and cellular membranes. Molecular dynamics simulation demonstrates the transition pathway from the intermediate state highlighted by the crystal structure into the final post-fusion conformation. Furthermore, the crystal structure conformation can be targeted by broadly neutralizing antibodies (bnAbs) recognizing the highly conserved membrane proximal external region (MPER). This corroborates that MPER bnAbs can block final steps of refolding of FP and TMR, which is required for completing membrane fusion.

Structure of HIV-1 gp41 with its membrane anchors targeted by neutralizing antibodies. Caillat C, Guilligay D, Torralba J, Friedrich N, Nieva JL, Trkola A, Chipot CJ, Dehez FL, Weissenhorn W. Elife 2021 Apr 19 ;10:e65005

Contact : W. Weissenhorn, UGA professor attached to the IBS (Entry and Budding of Enveloped Viruses Group)

Paleo biochemistry, a key to understanding the selection of enzyme properties

Studies providing insights into adaptative process of molecules to extreme conditions are of wide fundamental interest, as evolutionary processes impact the genomic organization, shape, function and phenotype of cells and their biomolecules. Thus evolutionary biochemistry allows to understand the fundamental process of exchange between the dynamic, structural and functional properties of enzymes.
In this work, scientists from the Institute of Structural Biology (IBS, Grenoble), in collaboration with the National Institute of Research in Digital Science and Technology (INRIA Rennes) and the Laboratory of Biometry and Evolutionary Biology (LBBE, Lyon), describe the evolutionary history (over a period of 500 million years) of malate dehydrogenases (MalDH) within Halobacteria, a metabolic enzyme facing extreme physicochemical conditions. They resurrected nine ancestors along the inferred halobacterial MalDH phylogeny and compared their biochemical properties with those of five modern halobacterial MalDHs. They found that a variety of evolutionary processes such as amino acid replacement, gene duplication, loss of MalDH gene and replacement owing to horizontal transfer resulted in significant differences in solubility, stability and catalytic. Unexpectedly, they analyzed that destabilizing mutations in a given circumstances could be at the origin of a gain of stability allowing a secondary adaptation in an environment with a very high pH. These researchers also showed the very important role of lateral gene transfer between species that allows a very rapid adaptive molecular response.
This work revealed that activity, stability and solubility of an enzyme are parameters that evolve independently of each other during an adaptive process.This is a fundamental finding that should be taken into account by researchers interested in protein engineering.

Resurrection of Ancestral Malate Dehydrogenases Reveals the Evolutionary History of Halobacterial Proteins : Deciphering gene trajectories and changes in biochemical properties. Samuel Blanquart, Mathieu Groussin, Aline Le Roy, Gergely J Szöllosi, Eric Girard, Bruno Franzetti, Manolo Gouy and Dominique Madern. Molecular Biology and Evolution, msab146, https://doi.org/10.1093/molbev/msab146

Contact : Dominique Madern (IBS/Extremophiles and Large Molecular Assemblies Group)

’Green’ chemistry and biofuels : Observing a photoenzyme at work

An international consortium* of scientists, including researchers from the IBS/DYNAMOP and IBS/SYN groups, has deciphered the mechanism and dynamics of the fatty acid photodecarboxylase (FAP) enzyme, a discovery published in Science on 08/04/2021. This photoenzyme is naturally present in many microscopic algae and uses light energy to catalyse the generation of hydrocarbons from fatty acids.
To elucidate the mechanism of this unique enzyme, the research teams have combined multi-faceted experimental and theoretical approaches comprising site-directed mutagenesis, time-resolved vibrational and electronic optical spectroscopies or cryotrapping of reaction intermediates, static and kinetic crystallography at synchrotrons and an X-ray free electron laser (XFEL) and quantum chemical calculations. The elucidation of the FAP catalytic mechanism and the identification of reaction intermediates and structural elements indispensable to its activity constitute a key basis for the optimization of the enzyme for the production of ‘green’ hydrocarbon fuels and chemicals that can be easily modulated by light. Press release.

* In France, this study mobilized researchers from the Institut de Biosciences et Biotechnologies Aix-Marseille in Cadarache, the Institut de Biologie Intégrative de la Cellule in Gif-sur-Yvette, the Institut Polytechnique de Paris in Palaiseau, the Institut de Biologie Structurale in Grenoble, the Universities of Lille and Rennes, the European Synchrotron Radiation Facility and the Institut Laue-Langevin. Abroad, researchers from the Max-Planck Institute in Heidelberg, Moscow State University and the SLAC National Accelerator Laboratory in Stanford are involved.

Mechanism and dynamics of fatty acid photodecarboxylase. Sorigué D, Hadjidemetriou K, Blangy S, Gotthard G, Bonvalet A, Coquelle N, Samire P, Aleksandrov A, Antonucci L, Benachir A, Boutet S, Byrdin M, Cammarata M, Carbajo S, Cuiné S, Doak RB, Foucar L, Gorel A, Grünbein M, Hartmann E, Hienerwadel R, Hilpert M, Kloos M, Lane TJ, Légeret B, Legrand P, Li-Beisson Y, Moulin S, Nurizzo D, Peltier G, Schirò G, Shoeman RL, Sliwa M, Solinas X, Zhuang B, Barends TRM, Colletier J-P, Joffre M, Royant A, Berthomieu C, Weik M, Domratcheva T, Brettel K, Vos MH, Schlichting I, Arnoux P, Müller P, Beisson F. Science 2021 ; 372:eabd5687 (https://science.sciencemag.org/content/372/6538/eabd5687/tab-pdf)

IBS Contact : Martin Weik

An Unexpected P-Cluster like Intermediate En Route to the Nitrogenase FeMo-co

Nitrogenase is a key metalloprotein that catalyzes the reduction of nitrogen to ammonia at room temperature and ambient pressure. It thus plays a major role in the global nitrogen cycle. It uses two metal centers : the P-cluster, an atypical [Fe₈S₇] center, which allows electron transfer to the active site itself, which is an organometallic [MoFe₇S₉C-(R)-homocitrate] center. Its biosynthesis requires the action of a dozen accessory proteins that constitute the NIF (for NItrogen Fixation) assembly machinery. The NifB protein is the key enzyme in this mechanism because it is responsible for the fusion of two [Fe₄S₄] centers combined with a carbide ion insertion and the addition of a sulfide ion to produce a [Fe₈S₉C] precursor termed NifB-co. Recently, American colleagues published a crystal structure of the NifB protein with all its metal centers. Unfortunately, they did not model their crystallographic data well and missed the identity of cluster bound to the active site. By reusing these data, we were able to highlight the presence of a unique [Fe₈S₈] center resulting from the fusion of [Fe₄S₄] centers. This crystal structure allowed us to redefine the order of the reaction steps showing that the FeS center fusion must take place before the carbide ion insertion. The particular coordination of this intermediate highlights the role of the protein matrix in the organization of the NifB-co biosynthetic steps, thus revealing the mechanism of the enzyme.

An unexpected P-cluster like intermediate en route to the nitrogenase FeMo-co. Leon P. Jenner, Mickael V. Cherrier, Patricia Amara, Luis M. Rubio and Yvain Nicolet. Chemical Science DOI : 10.1039/D1SC00289A

Contact : Yvain Nicolet (IBS/Metalloproteins Group)

IBS benefits from exceptional funding from the 3rd French Investment Program ’EquipEx+’

The 3rd French Investment Program ’EquipEx+’ aims to support new research equipment of international standard, to strengthen the excellence and competitiveness of French scientific research. Following a call for research proposals launched mid-2020, 50 proposals out of 135 were selected by an international jury end of 2020 for a total amount of 422 million euros.

IBS is associated with two of the winning projects :

• the FranceCryoeEM project for a "National instrumentation in cryo-electron microscopy" : 3 ultra-efficient and ultra-stable high-energy electron cryo-microscopes will be installed in France, one of them managed by IBS for the observation of macromolecules at atomic level,

• the MAGNIFIX project for a "Global upgrading and New French Hard X-Ray Investigation Infrastructures" : this project will give the French academic and industrial community privileged access to the new EBS-ESRF fourth generation synchrotron source (the most efficient in the world), through the upgrading of 5 French CRG "Collaborative Research Groups" beamlines (one managed by IBS) (total investment of 12 million euros over 2021-2025).

Pas de deux : how polymers keep dry proteins active

© Yann Fichou/IBS/CEA/CNRS/UGA

Dancing water molecules on the surface of soluble proteins provide the essential lubricant for macromolecular function. Surprisingly, polymers attached to protein surfaces have been reported to replace hydration water and bring inactive dry proteins back to life. The mechanism behind polymer-assisted functional protein motions has now been revealed by researchers from the Institut de Biologie Structurale in Grenoble, the Universities of Bordeaux, of California Irvine, of Bristol and of Perugia and from the Heinz-Maier Leibnitz Zentrum in Garching. The consortium applied neutron spectroscopy and molecular dynamics simulations to shed light on the motions animating proteins and polymers in the water-free hybrid. Separating them was possibly by selectively masking the signal from either the polymer or the protein by replacing hydrogen by deuterium atoms, the latter scattering neutrons two orders of magnitude less than the former in spectroscopy experiments. Surprisingly, protein and polymer motions turned out to be qualitatively similar, in stark contrast to protein and water motions being qualitatively different ; segmental polymer motions appear to substitute for hydration-water translational motions. Even if this substitution keeps dry proteins biologically active, certain dynamical modes are suppressed in the protein, possibly explaining the generally observed decrease in activity when hydration water is substituted by polymer coating. The study suggests ways to fine-tune polymer properties so that the loss in protein activity can be minimized. This will be particularly important for rationally designing protein-polymer hybrids for specific biotechnological applications, such as in medicine and cosmetics.

Diffusive-like motions in a solvent free protein-polymer hybrid. Schirò G, Fichou Y, Brogan APS, Sessions R, Lohstroh W, Zamponi M, Schneider GJ, Gallat F-X, Paciaroni A, Tobias DJ, Perriman A, Weik M. Physical Review Letters 126, 088102

Contact : Martin Weik & Giorgio Schirò (Dynamics and kinetics of molecular processes Group)

Supramolecular assembly of the Escherichia coli LdcI upon acid stress

Bacteria possess a sophisticated arsenal of defense mechanisms that allow them to survive in adverse conditions. Adaptation to acid stress and hypoxia is crucial for the enterobacterial transmission in the gastrointestinal tract of their human host. Using three-dimensional superresolution fluorescence microscopy and electron cryo-microscopy, the researchers of the MICA group, in collaboration with the PIXEL team and the M4D platform at the IBS, have shown that in response to acid stress, the enzyme lysine decarboxylase (LdcI) forms supramolecular assemblies in vivo in E. coli and polymerizes into filaments. They determined the atomic structure of those filaments in vitro and proposed a mechanistic model for LdcI function and offer tools for further in vivo investigations. This work has also made it possible to develop tools applicable to all types of cells, to study molecular assemblies by combining the two types of microscopy while preserving their structural integrity and their interactions with cellular partners.

Supramolecular assembly of the Escherichia coli LdcI upon acid stress. Jessop M, Liesche C, Felix J, Desfosses A, Baulard M, Adam V, Fraudeau A, Huard K, Effantin G, Kleman JP, Bacia-Verloop M, Bourgeois D, Gutsche I. Proc Natl Acad Sci U S A. 2021 Jan 12 ;118(2):e2014383118.

Congratulations to Andrea Carfi, former IBS PhD student, for the development of the Moderna’s COVID-19 vaccine

We are proud to announce that Andrea Carfi, currently VP & Head of Research for Infectious Disease at Moderna, Cambridge, MA, USA, is an IBS alumnus.

After receiving his doctorate under the direction of Otto Dideberg (retired) at the IBS in 1997 he completed his training as a postdoctoral fellow in Prof. Don Wiley’s group at Children’s Hospital (Harvard University) in Boston, MA, where he met the current IBS director Prof. W. Weissenhorn. Andrea Carfi then moved to industry, joining Merck in 2002. He returned to Cambridge (USA) in 2010 as a senior manager first at Novartis Vaccines and then GSK vaccines. He joined Moderna in 2017, where he contributed to the development of Moderna’s COVID-19 mRNA vaccine that was recently approved for use by the European Medicines Agency (https://www.ema.europa.eu/en/news/ema-recommends-covid-19-vaccine-moderna-authorisation-eu). The Moderna’s COVID19 vaccine has been approved and used in France since 11 January

To know more :

SARS-CoV-2 mRNA vaccine design enabled by prototype pathogen preparedness. Corbett KS, Edwards DK, Leist SR, Abiona OM, Boyoglu-Barnum S, Gillespie RA, Himansu S, Schäfer A, Ziwawo CT, DiPiazza AT, Dinnon KH, Elbashir SM, Shaw CA, Woods A, Fritch EJ, Martinez DR, Bock KW, Minai M, Nagata BM, Hutchinson GB, Wu K, Henry C, Bahl K, Garcia-Dominguez D, Ma L, Renzi I, Kong WP, Schmidt SD, Wang L, Zhang Y, Phung E, Chang LA, Loomis RJ, Altaras NE, Narayanan E, Metkar M, Presnyak V, Liu C, Louder MK, Shi W, Leung K, Yang ES, West A, Gully KL, Stevens LJ, Wang N, Wrapp D, Doria-Rose NA, Stewart-Jones G, Bennett H, Alvarado GS, Nason MC, Ruckwardt TJ, McLellan JS, Denison MR, Chappell JD, Moore IN, Morabito KM, Mascola JR, Baric RS, Carfi A, Graham BS. (2020). Nature ; 586(7830):567-571.

https://news.harvard.edu/gazette/story/2020/04/harvards-coronavirus-vaccine-efforts/ & https://masscpr.hms.harvard.edu/vaccines