Hermansky-Pudlak syndrome 1. This protein may play a role in organelle biogenesis associated with melanosomes, platelet dense granules, and lysosomes. The encoded protein is a component of three different protein complexes termed biogenesis of lysosome-related organelles complex (BLOC)-3, BLOC4, and BLOC5. Mutations in this gene are associated with Hermansky-Pudlak syndrome type 1. Multiple transcript variants encoding distinct isoforms have been identified for this gene; the full-length sequences of some of these have not been determined yet.