Required for the biogenesis of eye pigment granules (PubMed:10549280). Plays a role in vesicle-mediated protein trafficking to lysosomal compartments and in membrane docking/fusion reactions of late endosomes/lysosomes probably as part of the class C core vacuole/endosome tethering (CORVET) complex (PubMed:10549280, PubMed:22160599, PubMed:27253064). Component of the class C core vacuole/endosome tethering (CORVET) complex composed of at least dor/Vps18, Vps16A, Vps8 and car/Vps33A; unlike in other species, Vps11 is not part of the Drosophila complex (PubMed:27253064). Interacts with dor (PubMed:10549280). Interacts with ema (PubMed:20194640). Cytoplasmic, peripheral membrane protein associated with late endosomes/lysosomes. Expressed in larva and adult (at protein level). Flies display impaired deposition of pigment granules (PubMed:10549280). Member of the 'granule group' of eye color genes as mutants affect deposition in pigment granules of two types of pigments, the ommochromes and drosopterins (PubMed:10549280). RNAi-mediated knockdown results in late endosome fragmentation (PubMed:27253064). Belongs to the STXBP/unc-18/SEC1 family.