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Institut de Biologie StructuraleGrenoble / France

Highlights

A modified Fe-S cluster modulates [Ni-Fe] hydrogenase oxidative damage

Hydrogenases are enzymes of considerable interest for their potential biotechnological applications both as catalysts in biofuel cells and hydrogen producers. However, these applications can be greatly affected by their reactions with atmospheric oxygen. In order to better understand this problem, we have investigated a single mutation of the naturally O2-tolerant E. coli [NiFe] hydrogenase-1, which makes it O2-sensitive by changing its [4Fe-3S] cluster into a novel [4Fe-4S] cluster. Our theoretical study explains in detail the observed different redox properties of these two clusters and sheds considerable light on the biological solution to prevent O2-based deactivation.

X-ray structural, functional and computational studies of the O2-sensitive E. coli hydrogenase-1 C19G variant reveal an unusual [4Fe–4S] cluster. A. Volbeda, J. M. Mouesca, C. Darnault, M. M. Roessler, A. Parkin, F. A. Armstrong and J. C. Fontecilla-Camps. ChemComm; accepted 4th June 2018, DOI: 10.1039/c8cc02896f

C1q and MBL opsonins use a common anchor site on the CR1 receptor

Complement receptor type 1 (CR1) is a multi modular membrane receptor involved in the clearance of complement opsonized components from the blood stream. By binding targets tagged with complement-opsonins, the CR1 receptor on the surface of erythrocytes contributes to their elimination by transport to the liver, then phagocytosis by monocytes, macrophages or neutrophils.
CR1 is composed of 30 homologous complement control protein (CCP) modules and is a receptor for complement-opsonins C3b and C4b. While C3b and C4b have long been known as ligands of CR1, it is only recently that defense collagens such as mannose-binding lectin (MBL), ficolin-2, and C1q have also been shown to act as opsonins.
In this study, the IRPAS group located the attachment site of C1q and MBL to CR1 thanks to a molecular dissection strategy particularly adapted to the study of multi-modular proteins. The interaction site for both MBL and C1q is located on the same pair of modules CCP24-25 out of the 30 modules in CR1. This study contributes to enlarge knowledge on the multifunctional role of complement defense collagens and more especially on this new opsonin function that allows the transfer of foreign agents or altereded self on various receptors for clearance.

C1q and MBL interact with CR1 in the same region on CCP24-25 modules. Jacquet M, Cioci G, Fouët G, Bally I, Thielens NM, Gaboriaud C, Rossi V. Frontiers in Immunology;9, 453

How Detergent Impacts Membrane Proteins

Many cellular processes involve membrane proteins (MPs) and characterization of their structure, interactions and dynamics remains a challenge for structural biology. The difficulty is related to the need to extract these proteins from their biological membrane in order to study them. Detergents are frequently used but their physical properties differ from those of lipids and could alter the structural organization of MPs.
In this study, a family of membrane proteins, mitochondrial transporters, were analyzed in detail in a common detergent, dodecylphosphocholine (DPC). Several studies on these mitochondrial carriers in DPC had already proposed details on structure, dynamics and interactions and interpreted these observations from a biological perspective, but their biological relevance has been questionned. The NMR and MEMBRANE group studies, in collaboration with researchers at Nancy and Cambridge, combine NMR, biochemistry and MD simulation methods to resolve unambiguously this controversy. The results show a subtle balance of interactions between protein and detergent, which induces a significant disruption of the protein; the specificity of interaction with substrates is strongly impacted, and the protein samples partially unfolded conformations. A review of a number of structures obtained in DPC illustrates that these effects are relatively general, and helps clarify a debate on the impact of detergents.

1) How Detergent Impacts Membrane Proteins: Atomic-Level Views of Mitochondrial Carriers in Dodecylphosphocholine. Kurauskas V, Hessel A, Ma P, Lunetti P, Weinhäupl K, Imbert L, Brutscher B, King MS, Sounier R4, Dolce V, Kunji ERS, Capobianco L, Chipot C, Dehez F, Bersch B, Schanda P. Journal of Physical Chemistry Letters;9(5):933-938
2) Perturbations of Native Membrane Protein Structure in Alkyl Phosphocholine Detergents: A Critical Assessment of NMR and Biophysical Studies. Chipot C, Dehez F, Schnell JR, Zitzmann N, Pebay-Peyroula E, Catoire L, Miroux B, Kunji ERS, Veglia G, Cross TA, Schanda P. Chemical Reviews;118(7):3559-3607
3) Dynamics and interactions of ADP/ATP transporter AAC3 in DPC detergent are not functionally relevant. Kurauskas V, Hessel A, Dehez F, Chipot F, Bersch B, Schanda P. Nature Structural & Molecular Biology;doi: https://doi.org/10.1101/317669