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A comprehensive view of the archeal ESCRT-III machinery

Vendredi 4 décembre 2015 14:00 - Duree : 1 heure
Lieu : LAPM, Institut Jean Roget, Salle de Conférence du 5ème Etage, Faculté de Médecine-Pharmacie, Domaine de la Merci, La Tronche

Orateur : Patricia RENESTO (CNRS UMR 5163 – Joseph Fourier University)

Archaea comprise three major phyla Euryarchaeota, Crenarcheaota and Thaumarchaeota that exhibit some critical differences in major molecular mechanisms, such as DNA replication and cell division. Thus, Euryarchaeota and Thaumarchaeota division employs a bacterial-like FtsZ, apparatus whereas for Crenarchaeota, where FtsZ is lacking, cytokinesis relies on a newly discovered Cdv (for Cell division) machinery. Importantly, two of the three Cdv proteins, CdvB and CdvC are homologous of eukaryotic proteins belonging to the “endosomal sorting complex required for transport” (ESCRT) machinery, which catalyzes vesicle budding during endosomal protein sorting, budding of some enveloped viruses and cytokinesis. CdvB is a homologue of ESCRT-III, implicated in membrane fission and CdvC is a homologue of the AAAtype ATPase Vps4, required for ESCRT-III disassembly. The third member of the Cdv cluster, namely CdvA, is only present in Archaea. Several data reinforce the concept that archaeal Cdv proteins are closely related to the eukaryotic ESCRT-III counterparts.

Using Metallospherae sedula as model, our goal was to characterize the archaeal Cdv proteins. We evidenced for the first time that CdvA forms polymers in association with DNA, similar to known bacterial DNA partitioning proteins. We also observed that, in contrast to full-lengh CdvB that was purified as a monodisperse protein, the C-terminally deleted CdvB construct forms filamentous polymers, a phenomenon previously observed with eukaryotic ESCRT-III proteins. Finally, we solved a crystal structure for ring-shaped Vps4 from Metallosphera sedula refined to 3.6 Å resolution and which forms an asymmetric pseudohexamer, i.e. a trimer of dimers with three different inter-subunit interfaces. Conserved key residues within the different interfaces are shown to be important for MsVps4 assembly, ATPase activity in vitro, ESCRT-III disassembly in vitro and HIV-1 budding in vivo. This work on archaeal proteins thus offered the opportunity to determine the first X-ray structure of the oligomeric form of a Vps4-like protein and provides insight into the molecular motions the ringstructure undergoes in a concerted action to couple ATP hydrolysis to ESCRT-III substrate disassembly.

Contact : cordelia.bisanz@ujf-grenoble.fr

Discipline évènement : (Biologie / Chimie)
Entité organisatrice : (LAPM)
Nature évènement : (Séminaire)
Evènement répétitif : (Séminaire IJR)
Site de l'évènement : Pôle Santé / La Tronche

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