Institut de Biologie StructuraleGrenoble / France


ERC Advanced Grant 2019 for Martin Blackledge

The European Research Council (ERC) has awarded an "Advanced Grant" to Martin Blackledge, group leader of the Institut de Biologie Structurale (IBS - CEA/CNRS/UGA mixed research unit), for his project on the atomic resolution description of highly dynamic molecular assemblies and their role in viral replication.

Martin Blackledge is FDP group leader and Deputy Director at the IBS in Grenoble. His project entitled "DynamicAssemblies" will receive € 2.5 million financial support from the ERC over 5 years. Scientific excellence at European level is one of the main criteria for the selection of these awards dedicated to ground-breaking, high-risk projects presented by active leading Principal Investigators with a track-record of significant research achievements in the last 10 years.

Martin Blackledge studied physics at the University of Manchester and received his doctorate (D. Phil) in 1987 under the direction of Professor George Radda at the University of Oxford developing techniques for biomolecular NMR spectroscopy in vivo. In 1989 he received a Royal Society Fellowship to work at the ETH Zürich under the supervision of Professor Richard Ernst (Nobel prize for chemistry 1991) where he first started to develop methods to study biomolecular dynamics by NMR. Having discovered the beauty of the Alps, he decided to continue this work at the Institut de Biologie Structurale (CEA/CNRS/UGA) in Grenoble where he has headed the “Protein Dynamics and Flexibility by NMR” group since 2007.

The primary research interest of the Blackledge group is the study of protein dynamics by NMR, often combined with complementary biophysical techniques and advanced molecular simulation, to characterize the role of conformational flexibility in biological function on a broad range of time and length scales, from molecular recognition dynamics in folded proteins, to reorganizational dynamics of large multi-domain assemblies exhibiting extensive protein disorder to the study of fundamental physics underlying protein dynamics. He has published over 200 articles in this field. Most recently his group uses these techniques to describe highly flexible or intrinsically disordered proteins (IDPs), to map the thermodynamics and kinetics of their interaction trajectories at atomic resolution, and to determine the relationship between their dynamic behaviour and functional mechanism.

What is this project "DynamicAssemblies" about ?

IDPs are present throughout all known proteomes, playing important roles in functional mechanisms in all aspects of biology. Many molecular assemblies comprise highly dynamic components that are functionally essential. The elaboration of time-resolved, atomic resolution descriptions of the interaction trajectories of such highly disordered complexes, comprising both folded and disordered domains, is extremely challenging, requiring the development of adapted methodologies that can account for their intrinsic flexibility.
The project will in particular describe the structural and dynamic behaviour of highly disordered viral replication machines, including pre- and post-nucleocapsid assembly complexes, their interaction kinetics with host and viral partners, the effects of post-translational modifications, their assembly and functional mechanisms. The project will also identify the role of these IDPs in functional liquid droplets that provide a highly efficient means to spatially and temporally control essential molecular processes.
NMR spectroscopy is an exquisitely sensitive tool for studying highly dynamic molecular systems, allowing precise characterization of local and long-range conformational dynamics of IDPs and their complexes at atomic resolution. Ongoing development of NMR-based methods, combined with advances in fluorescence spectroscopy, cryoEM and SAS, underpinned by parallel developments in molecular simulation to ensure the necessary theoretical framework, will provide the essential tools to investigate the functional mechanisms of these previously inaccessible complexes.

Protein dynamics, NMR, intrinsically disordered proteins, phase separation, paramyxovirus, measles, nucleocapsid, self-assembly, molecular dynamics simulation, fluorescence

Amount of the award
€2.5 million for five years

High resolution structure determination of measles nucleocapsides

Measles virus is a highly contagious human pathogen that is experiencing a dangerous resurgence throughout the world, including Europe. Replication of the virus requires encapsidation of the RNA viral genome by the viral nucleoprotein, assembling into molecular suprastructures called nucleocapsids. Researchers at the IBS have developed experimental methods (1) to encapsidate specific RNA sequences in vitro, allowing the high resolution (3.3Å) three dimensional structure determination of these nucleocapsids using cryo-electron microscopy (2). This structure reveals the positions and interactions of the RNA molecule with respect to the nucleoprotein at the highest resolution yet achieved. Using this structure, the importance of specific amino acids in the RNA binding groove for the stability of the nucleocapsids was then demonstrated using Nuclear Magnetic Resonance and site-directed mutagenesis. Crucially, this structure also determines for the first time the register of binding of the RNA genome relative to the nucleocapsid, leading to fundamental new insight into the mechanisms underpinning RNA processing by the RNA polymerase complex.

(1) Self-assembly of measles virus nucleocapsid-like particles : Kinetics and RNA sequence dependence. Milles, Jensen, Communie, Maurin, Schoehn, Ruigrok, Blackledge. Angew Chem Int Ed 55, 9356 (2016)

(2) Assembly and cryo-EM structures of RNA-specific measles virus nucleocapsids provide mechanistic insight into paramyxoviral replication. Desfosses A, Milles S, Jensen MR, Guseva S, Colletier JP, Maurin D, Schoehn G, Gutsche I, Ruigrok RWH, Blackledge M. Proc Natl Acad Sci U S A. ; doi : 10.1073/pnas.1816417116.

Algal Remodeling in a Ubiquitous Planktonic Photosymbiosis

Photosymbiosis between single-celled hosts and microalgae is common in oceanic plankton. However, the functioning of this ecologically important cell-cell interaction and the subcellular mechanisms allowing the host to accommodate and benefit from its microalgae remain enigmatic. Here, using a combination of quantitative single-cell structural and chemical imaging techniques, a collaboration of researchers show that the structural organization, physiology, and trophic status of the algal symbionts (the haptophyte Phaeocystis) significantly change within their acantharian hosts compared to their free-living phase in culture. In symbiosis, algal cell division is blocked, photosynthesis is enhanced, and cell volume is increased by up to 10-fold with a higher number of plastids (from 2 to up to 30) and thylakoid membranes. This study unveils an unprecedented morphological and metabolic transformation of microalgae following their integration into a host, and it suggests that this widespread symbiosis is a farming strategy wherein the host engulfs and exploits microalgae.

The IBS-ISBG electron microscopy platform was involved in the preparation of the planctonic or cultured samples for electron microscopy imaging. An optimized sample preparation was also set up for correlative imaging between structural (TEM, SEM, FIB-SEM) and chemical imaging (X-ray fluorescence microscopy, SIMS).

Algal Remodeling in a Ubiquitous Planktonic Photosymbiosis. Decelle J, Stryhanyuk H, Gallet B, Veronesi G, Schmidt M, Balzano S, Marro S, Uwizeye C, Jouneau PH, Lupette J, Jouhet J, Maréchal E, Schwab Y, Schieber NL, Tucoulou R, Richnow H, Finazzi G, Musat N. Current Biology ; doi : 10.1016/j.cub.2019.01.073