Involved in early stages of melanosome biogenesis and maturation. Component of the biogenesis of lysosome-related organelles complex-2 (or BLOC2) composed of HPS3, HPS5 and HPS6. Interacts with HPS5 (PubMed:15030569). Interacts with HPS6 (PubMed:15030569, PubMed:25189619). Widely expressed. Higher levels of expression are observed in kidney, liver and placenta. The disease is caused by variants affecting the gene represented in this entry. Retina International's Scientific Newsletter HPS3 mutations