Sly1 protein bound to Golgi syntaxin Sed5p allows assembly and contributes to specificity of SNARE fusion complexes.
Fusion of transport vesicles with their target organelles involves specific membrane proteins, SNAREs, which form tight complexes bridging the membranes to be fused. Evidence from yeast and mammals indicates that Sec1 family proteins act as regulators of membrane fusion by binding to the target membrane SNAREs. In experiments with purified proteins, we now made the observation that the ER to Golgi core SNARE fusion complex could be assembled on syntaxin Sed5p tightly bound to the Sec1-related Sly1p. Sly1p also bound to preassembled SNARE complexes in vitro and was found to be part of a vesicular/target membrane SNARE complex immunoprecipitated from yeast cell lysates. This is in marked contrast to the exocytic SNARE assembly in neuronal cells where high affinity binding of N-Sec1/Munc-18 to syntaxin 1A precluded core SNARE fusion complex formation. We also found that the kinetics of SNARE complex formation in vitro with either Sly1p-bound or free Sed5p was not significantly different. Importantly, several presumably nonphysiological SNARE complexes easily generated with Sed5p did not form when the syntaxin was first bound to Sly1p. This indicates for the first time that a Sec1 family member contributes to the specificity of SNARE complex assembly.
Peng
Renwang
R
Department of Molecular Genetics, Max Planck Institute for Biophysical Chemistry, D-37070 Göttingen, Germany.
Gallwitz
Dieter
D
D002352:Carrier Proteins / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism* / Q000648:ultrastructure; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism* / Q000648:ultrastructure; D051938:Munc18 Proteins; D011485:Protein Binding / Q000502:physiology; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D022161:Transport Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D033921:Vesicular Transport Proteins; D015003:Yeasts / Q000166:cytology / Q000378:metabolism
D002352:Carrier Proteins; D005656:Fungal Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D051938:Munc18 Proteins; D050765:Qa-SNARE Proteins; C075137:SEC17 protein, S cerevisiae; C072520:SLY1 protein, S cerevisiae; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C077554:Sed5 protein, S cerevisiae; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D033921:Vesicular Transport Proteins