Understanding Periperal Membrane Protein Interactions | BPS Thematic Meeting

Understanding Peripheral Membrane Protein Interactions: Structure, Dynamics, Function and Therapy

Monday Speaker Abstracts

MEMBRANE INTERACTION OF A PROKARYOTIC ESCRT-III PROTEIN Lukas Schlösser 1 ; Mirka Kutzner 1 ; Benedikt Junglas 2 ; Sourav Maity 3 ; Nadja Hellmann 1 ; Wouter H Roos 3 ; Carsten Sachse 2 ; Dirk Schneider 1 ; 1 Johannes Gutenberg University, Department of Chemistry, Mainz, Germany 2 Forschungszentrum Jülich, Ernst-Ruska Centre for Microscopy and Spectroscopy with Electrons, Jülich, Germany 3 Rijksuniversiteit Groningen, Moleculaire Biofysica, Zernike Instituut, Groningen, The Netherlands The inner membrane-associated protein of 30 kDa (IM30) is involved in the biogenesis, protection and/or remodeling of internal membranes in cyanobacteria. The IM30 monomer consists of seven α -helices and spontaneously forms various homooligomeric barrel structures in solution. The oligomeric structure of IM30 exhibits a remarkable plasticity, which has also been observed with eukaryotic ESCRT-III proteins, the structural and functional homologs of IM30. In addition to barrels, we have observed the formation of rod structures in solution as well as carpets and spirals on membranes. Upon binding to solid-supported membranes, IM30 barrels disassemble into smaller oligomers, which involves partial unfolding of the monomers. In fact, the oligomeric assembly induces/stabilizes α -helical regions, and in IM30*, an IM30 variant defective in oligomerization, only a helical hairpin formed by the helices α 1-3 retains its ordered structure while the remaining regions are disordered. Membrane binding of IM30 monomers is followed by oligomerization and the formation of spiral structures on membrane surfaces, as also observed previously with eukaryotic ESCRT-III´s, as well as of barrel and rod structures. Membrane-attached IM30 barrels and rods can engulf membranes, and here membrane contacts appear to be mainly mediated by the N-terminal amphipathic helix α 0. Yet, the α 1-3 helical hairpin clearly is also involved in membrane binding in vitro and in vivo. Thus, while the N terminal helix α 0 of pro- and eukaryotic ESCRT-III´s is crucial for an interaction of ESCRT-III proteins with membranes within oligomeric assemblies, surface binding of monomeric ESCRT III subunits involves extended parts of the helix α 1-3 hairpin, the structured core conserved in all ESCRT-III superfamily members. Our findings support a conserved membrane-binding and remodeling mechanism across the ESCRT-III superfamily, shared between prokaryotic and eukaryotic proteins.

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