Rab effector protein involved in melanosome transport. Serves as link between melanosome-bound RAB27A and the motor proteins MYO5A and MYO7A. May link RAB27A-containing vesicles to actin filaments. Functions as a protein kinase A-anchoring protein (AKAP). May act as a scaffolding protein that links PKA to components of the exocytosis machinery, thus facilitating exocytosis, including insulin release (By similarity). Binds MYO5A, MYO7A and F-actin (By similarity). Binds RAB27A that has been activated by GTP-binding via its N-terminus. Interacts with PRKAR2A. Interacts with components of the exocyst complex, including EXOC3 and EXOC4 (By similarity). In presynaptic and postsynaptic areas in photoreceptor cells and in the basal microvilli of retinal pigment epithelium cells. Associated with melanosomes. Colocalizes with actin filaments. Detected in brain, skin, heart, adrenal medulla, pancreas, intestine, liver, kidney, muscle and testis.