Complete Amino Acid Sequence of the Precursor Region of Rat Prolactin

Rat preprolactin was translated in a wheat germ in vitro synthetic system in the presence of 3H-labeled amino acids. The amino-terminal sequence of the radiolabeled precursor was quantitatively identified by high pressure liquid chromatography. The 29 residue precursor sequence is: Met-Asn-Ser-Gln-Val-Ser-Ala-Arg-Lys-Ala-Gly-Thr-Leu-Leu-Leu-Leu-Met-Met-Ser-Asn-Leu-Leu-Phe-Cys-Gln-Asn-Val-Gln-Thr-. A discussion of the structure-function relationships of the precursor region and the microsequencing methods used to determine the sequence is presented. The amino-terminal 30 residue sequence of the secreted form of rat prolactin was determined and found to differ at positions 7 and 8 (-Gly-Asp-) from a previously reported rat prolactin sequence (Parlow, A. F., & Shome, B. (1976) Fed. Proc., Fed. Am. Soc. Exp. Biol. 35, 219).