Structure and disassembly of filaments formed by the ESCRT-III subunit Vps24 |
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Authors: | Ghazi-Tabatabai Sara Saksena Suraj Short Judith M Pobbati Ajaybabu V Veprintsev Dmitry B Crowther R Anthony Emr Scott D Egelman Edward H Williams Roger L |
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Affiliation: | MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK. |
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Abstract: | The ESCRT machinery mediates sorting of ubiquitinated transmembrane proteins to lysosomes via multivesicular bodies (MVBs) and also has roles in cytokinesis and viral budding. The ESCRT-III subunits are metastable monomers that transiently assemble on membranes. However, the nature of these assemblies is unknown. Among the core yeast ESCRT-III subunits, Snf7 and Vps24 spontaneously form ordered polymers in vitro. Single-particle EM reconstruction of helical Vps24 filaments shows both parallel and head-to-head subunit arrangements. Mutations of regions involved in intermolecular assembly in vitro result in cargo-sorting defects in vivo, suggesting that these homopolymers mimic interactions formed by ESCRT-III heteropolymers during MVB biogenesis. The C terminus of Vps24 is at the surface of the filaments and is not required for filament assembly. When this region is replaced by the MIT-interacting motif from the Vps2 subunit of ESCRT-III, the AAA-ATPase Vps4 can both bundle and disassemble the chimeric filaments in a nucleotide-dependent fashion. |
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