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Syntaxin-Binding Protein 1 (STXBP1), encoded by a gene of the same name, is a protein considered part of the Sec1/Munc18 family of proteins. In this picture, there are actually two chains, A and B. These chains represent two sequence-unique entities. Chain A (pictured in grey), which is the STXBP1 strand, consists of 590 amino acid residues. Of these, 248 residues make up 26 alpha helices while 80 residues make up 23 strands of beta sheet. This peptide chain is in the L conformation meaning it is a mirror image of the D conformation while maintaining the same sequence. Chain B (pictured in green) is actually syntaxin A1 already bound to the STXBP1, and it contains 242 total residues. 170 residues make up 8 alpha helices here and one residue is responsible for one beta sheet. These two chains can be bound a in two different ways: to the N-terminus which is thought to cause interactions with SNARE proteins, and via a "closed" conformation which is thought to inhibit interactions.

Function

STXBP1 is responsible for the regulation of membrane fusion through interactions with the family of SNARE proteins, syntaxin. The syntaxin assembles SNARE complexes which contain an open conformation of syntaxin A1. This complex, as well as a closed formation of syntaxin A1, interacts with STXBP1 causing interactions and inhibiting interactions respectively.

Disease

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