This superfamily entry represents domain 3b which is well conserved across SM protein structures, such as Munc18-2, Vps33A. 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) PMID:8769846. The Sec1/Munc18 protein family contains proteins associated with vesicle transport, regulating these processes by binding to t-SNARE homologues of syntaxin with high affinity. Linked to this superfamily are syntaxin-binding protein FunFams. In eukaryotic cells, the movement of macromolecules between their membrane-bound compartments is a highly regulated process controlled by multi-subunit protein sorting complexes. The mammalian HOPS complex is one such example and it comprises six subunits (Vps11, Vps16, Vps18, Vps33A, Vps39, and Vps41). Human Vps33A is predicted to be a member of the Sec1/Munc18 (SM) family of proteins that, together with SNAREs, comprise the core machinery essential for membrane fusion in eukaryotes.

INTERPRO:IPR027482, INTERPRO:IPR036045, PFAM:PF00995,PMID:8769846,PMID:23901104,PMID:24194549,PMID:21876177,PMID:12426383,DOI:10.1016/S0969-2126(00)00156-8