Particular processing of pro-opiomelanocortin in Xenopus laevis intermediate pituitary. Sequencing of alpha- and beta-melanocyte-stimulating hormones.

alpha- and beta-melanocyte-stimulating hormones (alpha-MSH and beta-MSH) have been isolated from Xenopus laevis neurointermediate pituitary and microsequenced. Intracellular alpha-MSH is not N-acetylated after proteolytic processing of pro-opiomelanocortin in contrast to mammalian alpha-MSHs. There is a high preservation of the melanotropic amino acid sequence common to all MSHs although in Xenopus beta-MSH a histidine residue replaces the glutamic acid residue found in position 8 of mammalian beta-MSHs.