P protein is a protein  encoded by the OCA2 gene. The P protein is believed to be an integral membrane protein involved in small molecule transport, specifically tyrosine - a precursor of melanin. Certain mutations in OCA2 result in type 2 oculocutaneous albinism. Another mutation in the OCA2 is found common to nearly all people with blue eyes, and has been hypothesized that all blue eyed humans share a single common ancestor with whom the mutation originated.

Tyrosinase-positive oculocutaneous albinism (OCA, type II) is an autosomal recessive disorder in which the biosynthesis of melanin pigment is reduced in skin, hair, and eyes. Although affected infants may appear at birth to have OCA type I, or complete absence of melanin pigment, most patients with OCA type II acquire small amounts of pigment with age.