This family consists of several eukaryotic synaphin 1 and 2 proteins. Synaphin/complexin is a cytosolic protein that preferentially binds to syntaxin within the SNARE complex. Synaphin promotes SNAREs to form precomplexes that oligomerise into higher order structures. A peptide from the central, syntaxin binding domain of synaphin competitively inhibits these two proteins from interacting and prevents SNARE complexes from oligomerising. It is thought that oligomerisation of SNARE complexes into a higher order structure creates a SNARE scaffold for efficient, regulated fusion of synaptic vesicles [1]. Synaphin promotes neuronal exocytosis by promoting interaction between the complementary syntaxin and synaptobrevin transmembrane regions that reside in opposing membranes prior to fusion [2].

1: SNARE complex oligomerization by synaphin/complexin is essential for synaptic vesicle exocytosis. Tokumaru H, Umayahara K, Pellegrini LL, Ishizuka T, Saisu H, Betz H, Augustine GJ, Abe T; Cell 2001;104:421-432. PMID:11239399

2: Action of complexin on SNARE complex. Hu K, Carroll J, Rickman C, Davletov B; J Biol Chem 2002;277:41652-41656. PMID:12200427