Melanophilin (MLPH) is a member of the exophilin subfamily of Rab effector proteins. MLPH is a modular protein,forming a ternary complex with the small Ras-related GTPase Rab27A in its GTP-bound form and the motor protein myosin Va. It regulates retention of melanosomes at the peripheral actin cytoskeleton of melanocytes,a process essential for normal mammalian pigmentation. Defects in MLPH are a cause of Griscelli syndrome type 3 (GS3),which is characterized by a silver-gray hair color and abnormal pigment distribution in the hair shaft.