CHARACTERIZATION OF THE CDNA-ENCODING PROOPIOMELANOCORTIN IN THE FROG RANA-RIDIBUNDA

In the amphibian pars intermedia, secretion of proopiomelanocortin (POMC)-derived peptides is controlled by multiple factors including classical neurotransmitters and neuropeptides. To pursue questions concerning the regulation of POMC gene expression in Rana ridibunda, we have isolated and characterized a full-length cDNA for frog POMC. A cDNA clone isolated from a frog pituitary library contains an open-reading frame of 780-bp that predicts a 260 amino acid POMC protein. The structure of frog POMC demonstrates considerable amino acid sequence similarity with POMC from other species. In particular, the sequence of α-melanotropin (α-MSH) is identical in frog and all mammalian species studied so far, while adrenocorticotropin (ACTH) and β-endorphin exhibit 79% and 84% homology with their human counterpart. Frog POMC contains only one potential asparagine-linked N-glycosylation signal (Asn-Ser-Thr) within the γ-MSH domain. The α-MSH sequence is C-terminally flanked by the Gly-Lys-Lys amidation signal while the joining peptide is not amidate. © 1990 Academic Press, Inc.