syntaxin

Syntaxins are a family of membrane integrated Q-SNARE proteins participating in exocytosis.

== Domains == Syntaxins possess a single C-terminal transmembrane domain, a SNARE domain (known as H3), and an N-terminal regulatory domain (Habc). Syntaxin 17 may have two transmembrane domains. The SNARE (H3) domain binds to both synaptobrevin and SNAP-25 forming the core SNARE complex. Formation of this stable SNARE core complex is believed to generate the free energy required to initiate fusion between the vesicle membrane and plasma membrane. The N-terminal Habc domain is formed by 3 α-helices and when collapsed onto its own H3 helix forms an inactive "closed" syntaxin conformation. This closed conformation of syntaxin is believed to be stabilized by binding of Munc-18 (nSec1), although more recent data suggests that nSec1 may bind to other conformations of syntaxin, as well. The "open" syntaxin conformation is the conformation that is competent to form into SNARE core complexes.