Receptor for MSH (alpha, beta and gamma) and ACTH (By similarity). The activity of this receptor is mediated by G proteins which activate adenylate cyclase (By similarity). Mediates melanogenesis, the production of eumelanin (black/brown) and phaeomelanin (red/yellow), via regulation of cAMP signaling in melanocytes (PubMed:9799269). Interacts with MGRN1, but does not undergo MGRN1-mediated ubiquitination; this interaction competes with GNAS-binding and thus inhibits agonist-induced cAMP production. Interacts with OPN3; the interaction results in a decrease in MC1R-mediated cAMP signaling and ultimately a decrease in melanin production in melanocytes. Variation is correlated with coat color. MC1R*2 is associated with the black color of European large black and Chinese meishan pigs. MC1R*3 is associated with the black color in the hampshire breed. MC1R*4 is found in recessive red animals. Belongs to the G-protein coupled receptor 1 family.