Sec9 is a SNAP-25-like component of a yeast SNARE complex that may be the effector of Sec4 function in exocytosis.
To identify potential Sec4 effectors, we isolated high copy suppressors of a Sec4 effector domain mutant. The most potent of these was found to be SEC9, a gene required for post-Golgi transport. The sole essential domain of Sec9 has significant sequence similarity to the neuronal protein SNAP-25, a component of the SNARE complex, that is implicated in vesicle targeting and fusion. Analogous to SNAP-25, Sec9 is bound to the yeast plasma membrane and is absent from post-Golgi vesicles. Furthermore, Sec9 is physically associated with two proteins that are homologous to components of the neuronal SNARE complex. Our results identify Sec9 as the yeast cognate of SNAP-25 and suggest that SNARE complexes acting at specific stages of vesicular transport serve as the ultimate targets of regulation by members of the Sec4/Ypt1/Rab family of GTPases.
Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8002.
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Brennwald
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Kearns
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Champion
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Keränen
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Bankaitis
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Novick
D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D005089:Exocytosis; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000378:metabolism / Q000502:physiology; D050765:Qa-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013329:Structure-Activity Relationship; D050825:Synaptosomal-Associated Protein 25; D020691:rab GTP-Binding Proteins
D005656:Fungal Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; C090117:SEC9 protein, S cerevisiae; C084006:SSO1 protein, S cerevisiae; C084007:SSO2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D050825:Synaptosomal-Associated Protein 25; D019204:GTP-Binding Proteins; C064320:SEC4 protein, S cerevisiae; D020691:rab GTP-Binding Proteins