DETECTION OF A NOVEL SEQUENCE CHANGE IN THE MAJOR FORM OF ALPHA-MSH ISOLATED FROM THE INTERMEDIATE PITUITARY OF THE REPTILE, ANOLIS-CAROLINENSIS

Intermediate pituitaries of the reptile, Anolis carolinensis, were separately pulse labeled with [H-3]Trp and [H-3]Tyr. The major form of alpha-MSH was purified by immunoprecipitation and isolated by reverse phase HPLC. Tryptic peptide analysis indicated that the [H-3]Trp-labeled C-terminal fragment of Anolis alpha-MSH had the same retention time as mammalian ACTH(9-13) amide; however, the [H-3]Tyr-labeled N-terminal fragment did not coelute with either mammalian ACTH(1-8) or N-acetyl-ACTH(1-8). Purification of alpha-MSH from 76 Anolis intermediate pituitaries confirmed that a sequence change had occurred in the N-terminal region of Anolis alpha-MSH. The tissues were acid extracted and purified by Sephadex G-25 chromatography and reverse phase HPLC to yield 4.5-mu-g of purified Anolis alpha-MSH for amino acid composition analysis and automated Edman degradation sequence analysis. The major form of Anolis alpha-MSH is nonacetylated and has the following novel primary sequence: Ser-Tyr-Ala-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro(Val-amide). The presence of Val-amide was verified by immunological analysis, tryptic peptide analysis and amino acid composition analysis.