A novel snare N-terminal domain revealed by the crystal structure of Sec22b.
Intra-cellular membrane fusion is facilitated by the association of SNAREs from opposite membranes into stable alpha-helical bundles. Many SNAREs, in addition to their alpha-helical regions, contain N-terminal domains that likely have essential regulatory functions. To better understand this regulation, we have determined the 2.4-A crystal structure of the 130-amino acid N-terminal domain of mouse Sec22b (mSec22b), a SNARE involved in endoplasmic reticulum/Golgi membrane trafficking. The domain consists of a mixed alpha-helical/beta-sheet fold that resembles a circular permutation of the actin/poly-proline binding protein, profilin, and the GAF/PAS family of regulatory modules. The structure is distinct from the previously characterized N-terminal domain of syntaxin 1A, and, unlike syntaxin 1A, the N-terminal domain of mSec22b has no effect on the rate of SNARE assembly in vitro. An analysis of surface conserved residues reveals a potential protein interaction site. Key residues in this site are distinct in two mammalian Sec22 variants that lack SNARE domains. Finally, sequence analysis indicates that a similar domain is likely present in the endosomal/lysosomal SNARE VAMP7.
Gonzalez
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LC
Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute and the Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA.
Weis
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Scheller
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RH
D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism; D017124:Conserved Sequence; D003285:Contractile Proteins; D003461:Crystallography; D008565:Membrane Proteins / Q000737:chemistry*; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism; D051304:Profilins; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D050683:R-SNARE Proteins; D011956:Receptors, Cell Surface / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1
D000954:Antigens, Surface; D003285:Contractile Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; C495739:Pfn1 protein, mouse; D051304:Profilins; D050683:R-SNARE Proteins; D011956:Receptors, Cell Surface; C494212:STX1A protein, human; D029701:Saccharomyces cerevisiae Proteins; C106909:Sec22 protein, S cerevisiae; C432415:Sec22b protein, mouse; C494209:Snap25 protein, mouse; C494214:Stx1a protein, mouse; C496927:Sybl1 protein, mouse; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1