TitleHOPS proofreads the trans-SNARE complex for yeast vacuole fusion.
Publication TypeJournal Article
Year of Publication2008
AuthorsStarai, VJ, Hickey, CM, Wickner, W
JournalMol Biol Cell
Volume19
Issue6
Pagination2500-8
Date Published2008 Jun
ISSN1939-4586
KeywordsAdenosine Triphosphate, Amino Acid Motifs, Multiprotein Complexes, Protein Structure, Tertiary, Protein Transport, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, SNARE Proteins, Vacuoles
Abstract

The fusion of yeast vacuoles, like other organelles, requires a Rab-family guanosine triphosphatase (Ypt7p), a Rab effector and Sec1/Munc18 (SM) complex termed HOPS (homotypic fusion and vacuole protein sorting), and soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). The central 0-layer of the four bundled vacuolar SNAREs requires the wild-type three glutaminyl (Q) and one arginyl (R) residues for optimal fusion. Alterations of this layer dramatically increase the K(m) value for SNAREs to assemble trans-SNARE complexes and to fuse. We now find that added purified HOPS complex strongly suppresses the fusion of vacuoles bearing 0-layer alterations, but it has little effect on the fusion of vacuoles with wild-type SNAREs. HOPS proofreads at two levels, inhibiting the formation of trans-SNARE complexes with altered 0-layers and suppressing the ability of these mismatched 0-layer trans-SNARE complexes to support membrane fusion. HOPS proofreading also extends to other parts of the SNARE complex, because it suppresses the fusion of trans-SNARE complexes formed without the N-terminal Phox homology domain of Vam7p (Q(c)). Unlike some other SM proteins, HOPS proofreading does not require the Vam3p (Q(a)) N-terminal domain. HOPS thus proofreads SNARE domain and N-terminal domain structures and regulates the fusion capacity of trans-SNARE complexes, only allowing full function for wild-type SNARE configurations. This is the most direct evidence to date that HOPS is directly involved in the fusion event.

DOI10.1091/mbc.E08-01-0077
Alternate JournalMol. Biol. Cell
Department Authors: 
Vincent J. Starai
Lab Association: 
Starai
Research Areas: 
Molecular Microbiology
Microbial Physiology