InterPro domain: IPR027482

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 entry represents domain 2 from the Sec1 family which includes Sec1, Sly1, Slp1/Vps33, yeast Vps45/Stt10, Unc-18 from nematodes, Munc-18b/muSec1, Munc-18c from mouse, Rop from Drosophila, Munc-18/n-Sec1/rbSec1A and rbSec1B from rat [ 4 , 5 , 6 , 7 ].

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
4. Structural basis for the Golgi membrane recruitment of Sly1p by Sed5p. EMBO J. 21, 6114-24
5. Structural basis of Vps33A recruitment to the human HOPS complex by Vps16. Proc Natl Acad Sci U S A 110, 13345-50
6. Syntaxin binding mechanism and disease-causing mutations in Munc18-2. Proc Natl Acad Sci U S A 110, E4482-91
7. Primordial neurosecretory apparatus identified in the choanoflagellate Monosiga brevicollis. Proc. Natl. Acad. Sci. U.S.A. 108, 15264-9