The endosomal sorting complex ESCRT-II mediates the assembly and architecture of ESCRT-III helices.
The endosomal sorting complexes required for transport (ESCRTs) constitute hetero-oligomeric machines that mediate topologically similar membrane-sculpting processes, including cytokinesis, retroviral egress, and multivesicular body (MVB) biogenesis. Although ESCRT-III drives membrane remodeling that creates MVBs, its structure and the mechanism of vesicle formation are unclear. Using electron microscopy, we visualize an ... ESCRT-II:ESCRT-III supercomplex and propose how it mediates vesicle formation. We define conformational changes that activate ESCRT-III subunit Snf7 and show that it assembles into spiraling ~9 nm protofilaments on lipid monolayers. A high-content flow cytometry assay further demonstrates that mutations halting ESCRT-III assembly block ESCRT function. Strikingly, the addition of Vps24 and Vps2 transforms flat Snf7 spirals into membrane-sculpting helices. Finally, we show that ESCRT-II and ESCRT-III coassemble into ~65 nm diameter rings indicative of a cargo-sequestering supercomplex. We propose that ESCRT-III has distinct architectural stages that are modulated by ESCRT-II to mediate cargo capture and vesicle formation by ordered assembly.
Mesh Terms:
Endosomal Sorting Complexes Required for Transport, Multivesicular Bodies, Mutation, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Transport Vesicles
Endosomal Sorting Complexes Required for Transport, Multivesicular Bodies, Mutation, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Transport Vesicles
Cell
Date: Oct. 12, 2012
PubMed ID: 23063125
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