Complexins: cytosolic proteins that regulate SNAP receptor function.
A family of proteins called complexins was discovered that compete with alpha-SNAP, but not synaptotagmin, for SNAP receptor binding. Complexins I and II are highly homologous hydrophilic proteins that are tightly conserved, with 100% identity among mouse, rat, and human complexin II. They are enriched in neurons where they colocalize with syntaxin and SNAP-25; in addition, complexin II is expressed ubiquitously at low levels. Complexins bind weakly to syntaxin alone and not at all to synaptobrevin and SNAP-25, but strongly to the SNAP receptor-core complex composed of these three molecules. They compete with alpha-SNAP for binding to the core complex but not with other interacting molecules, including synaptotagmin I, suggesting that the complexins regulate the sequential interactions of alpha-SNAP and synaptotagmins with the SNAP receptor during exocytosis.
McMahon
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HT
Howard Hughes Medical Institute, University of Texas Southwestern Medical School, Dallas 75235, USA.
Missler
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Li
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Südhof
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TC
D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D001923:Brain Chemistry; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000378:metabolism; D003600:Cytosol / Q000737:chemistry; D005089:Exocytosis; D015870:Gene Expression; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D046911:Macromolecular Substances; D008561:Membrane Fusion / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D009474:Neurons / Q000737:chemistry; D050683:R-SNARE Proteins; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050600:SNARE Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D013045:Species Specificity; D013572:Synaptic Vesicles / Q000378:metabolism*; D050825:Synaptosomal-Associated Protein 25; D050863:Synaptotagmin I; D050857:Synaptotagmins; D033921:Vesicular Transport Proteins
D033942:Adaptor Proteins, Vesicular Transport; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins; C494208:SNAP25 protein, human; D050600:SNARE Proteins; C494310:SYT1 protein, human; C494209:Snap25 protein, mouse; C494210:Snap25 protein, rat; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D050825:Synaptosomal-Associated Protein 25; D050863:Synaptotagmin I; C494311:Syt1 protein, mouse; C494312:Syt1 protein, rat; D033921:Vesicular Transport Proteins; C095992:complexin I; C095993:complexin II; D050857:Synaptotagmins; D002118:Calcium