InterPro domain: IPR043154

Sec1-like molecules have been implicated in a variety of eukaryotic vesicle transport processes including neurotransmitter release by exocytosis [ 1 ].They regulate vesicle transport by binding to a t-SNARE from the syntaxin family. This process is thought to prevent SNARE complex formation, a protein complex required for membrane fusion. Whereas Sec1 molecules are essential for neurotransmitter release and other secretory events, their interaction with syntaxin molecules seems to represent a negative regulatory step in secretion [ 2 ].

The nSec1 polypeptide chain can be divided into three domains. The first domain, consists of a five-stranded parallel beta-sheet flanked by five alpha-helices. The second domain, like the first one, has an alpha-beta-alpha fold, however the beta-sheet of domain 2 features five parallel strands with an additional antiparallel strand on one edge. The third domain is a large insertion between the third and fourth parallel strands of domain 2, and can be subdivided in two [ 3 ].

This superfamily represents the domain 1 of Sec1 and related proteins.

Members of the Sec1 family include Sec1, Sly1, Slp1/Vps33, Vps45/Stt10 (yeast), Unc-18 (nematode), Munc-18b/muSec1, Munc-18c (mouse), Rop (Drosophila), Munc-18/n-Sec1/rbSec1A and rbSec1B (rat) [ 4 ].

1. The Sec1 family: a novel family of proteins involved in synaptic transmission and general secretion. J. Neurochem. 66, 889-97
2. The X-ray crystal structure of neuronal Sec1 from squid sheds new light on the role of this protein in exocytosis. Structure 8, 685-94
3. Three-dimensional structure of the neuronal-Sec1-syntaxin 1a complex. Nature 404, 355-62