title: An intramolecular t-SNARE complex functions in vivo without the syntaxin NH2-terminal regulatory domain.
abstract: Membrane fusion in the secretory pathway is mediated by SNAREs (located on the vesicle membrane [v-SNARE] and the target membrane [t-SNARE]). In all cases examined, t-SNARE function is provided as a three-helix bundle complex containing three approximately 70-amino acid SNARE motifs. One SNARE motif is provided by a syntaxin family member (the t-SNARE heavy chain), and the other two helices are contributed by additional t-SNARE light chains. The syntaxin family is the most conformationally dynamic group of SNAREs and appears to be the major focus of SNARE regulation. An NH2-terminal region of plasma membrane syntaxins has been assigned as a negative regulatory element in vitro. This region is absolutely required for syntaxin function in vivo. We now show that the required function of the NH2-terminal regulatory domain (NRD) of the yeast plasma membrane syntaxin, Sso1p, can be circumvented when t-SNARE complex formation is made intramolecular. Our results suggest that the NRD is required for efficient t-SNARE complex formation and does not recruit necessary scaffolding factors.
authors.affiliation: Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251, USA.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Van Komen
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Bai
authors.forename: Brenton L
authors.initials: BL
authors.lastname: Scott
authors.forename: James A
authors.initials: JA
authors.lastname: McNew
mesh_terms: D000595:Amino Acid Sequence; D008561:Membrane Fusion / Q000502:physiology*; D046912:Multiprotein Complexes; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D050765:Qa-SNARE Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D050767:Qc-SNARE Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D050600:SNARE Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D046912:Multiprotein Complexes; D050765:Qa-SNARE Proteins; D050767:Qc-SNARE Proteins; D011993:Recombinant Fusion Proteins; C090117:SEC9 protein, S cerevisiae; D050600:SNARE Proteins; C084006:SSO1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins