UniProt ID: P59015
FUNCTION: Plays a role in vesicle-mediated protein trafficking to lysosomal compartments including the endocytic membrane transport pathways. Believed to act as a core component of the putative HOPS endosomal tethering complex which is proposed to be involved in the Rab5-to-Rab7 endosome conversion probably implicating MON1A/B, and via binding SNAREs and SNARE complexes to mediate tethering and docking events during SNARE-mediated membrane fusion (By similarity). May be involved in vesicle trafficking to the hepatocyte apical membrane and play a role in development of the intra-hepatic biliary tree. May target endosomes to the pigment granule in melanocytes. Essential for early embryonic development. {ECO:0000250|UniProtKB:Q9P253, ECO:0000269|PubMed:12006978, ECO:0000269|PubMed:16000385}.
SUBUNIT: Component of the homotypic fusion and vacuole protein sorting (HOPS) complex (By similarity). {ECO:0000250|UniProtKB:Q9P253}.
SUBCELLULAR LOCATION: Late endosome membrane {ECO:0000250|UniProtKB:Q9P253}; Peripheral membrane protein {ECO:0000250|UniProtKB:Q9P253}; Cytoplasmic side {ECO:0000250|UniProtKB:Q9P253}. Lysosome membrane {ECO:0000250|UniProtKB:Q9P253}; Peripheral membrane protein {ECO:0000250|UniProtKB:Q9P253}; Cytoplasmic side {ECO:0000250|UniProtKB:Q9P253}. Note=Cytoplasmic, peripheral membrane protein associated with early endosomes and late endosomes/lysosomes.
DISRUPTION PHENOTYPE: Mutants display hepatomegaly associated with large, vesicle-filled hepatocytes. They also have defects in pigmentation with reduced numbers of melanophores and no iridophores. {ECO:0000269|PubMed:16000385}.
SIMILARITY: Belongs to the VPS18 family. {ECO:0000305}.
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