Endocrinology, Vol 126, 3271-3273, Copyright © 1990 by Endocrine Society

ARTICLES

Identification of a novel family of growth hormone-related proteins secreted by rat placenta

S Ogilvie, WC Buhi, JA Olson and KT Shiverick
Department of Pharmacology, University of Florida, Gainesville 32610.

Mid-to-late gestation rat placenta synthesizes a number of proteins related to prolactin, including rat placental lactogen II (rPL-II), rat prolactin-like protein A (rPLP-A) and rat prolactin-like protein B (rPLP-B). This study identifies a new family of proteins synthesized and secreted by gestation day 15 placental explants which exhibit amino acid homology to growth hormone precursors from several species. Placental explant medium was fractionated by ammonium sulfate precipitation and analyzed by two-dimensional SDS-polyacrylamide gel electrophoresis to isolate four distinct proteins with Mr values of 28,000, 23,000, 25,000 and 30,000 and pI values of 5.7, 5.7, 5.4 and 5.3, respectively. These proteins represent a major fraction of secretory proteins with Mr in the 20,000 to 30,000 range. Immunoblot analysis showed that none of the four proteins crossreacted with antipeptide antisera against rPL-II, rPLP-A, or rPLP-B. These proteins were electrophoretically transferred from two-dimensional SDS- polyacrylamide gels onto an Immobilon PVDF membrane and N-terminal amino acid microsequencing carried out with a gas phase sequencer. N- terminal sequences of 45, 37, 37 and 32 amino acid residues were identified for proteins 1, 2, 3 and 4, respectively. The four proteins exhibit 76% to 97% homology. Computer analysis further revealed a 28% identity in a 32 amino acid overlap which begins at residue 14 of the 28,000 Mr protein (protein 1) and at residue 31 of growth hormone precursors of rat, mouse and human. The 32 amino acid overlap is 78% homologous if conservative amino acid replacements are included.

This article has been cited by other articles:

				G. Dai, M. W. Wolfe, and M. J. Soares Distinct Regulatory Regions from the Prolactin-Like Protein C Variant Promoter Direct Trophoblast Giant Cell Versus Spongiotrophoblast Cell-Specific Expression Endocrinology, October 1, 1999; 140(10): 4691 - 4698. [Abstract] [Full Text]

				K. Iwatsuki, M. Oda, W. Sun, S. Tanaka, T. Ogawa, and K. Shiota Molecular Cloning and Characterization of a New Member of the Rat Placental Prolactin (PRL) Family, PRL-Like Protein H Endocrinology, December 1, 1998; 139(12): 4976 - 4983. [Abstract] [Full Text] [PDF]

				G. Dai, B. M. Chapman, B. Liu, K. E. Orwig, D. Wang, R. A. White, B. Preuett, and M. J. Soares A New Member of the Mouse Prolactin (PRL)-Like Protein-C Subfamily, PRL-Like Protein-C{alpha}: Structure and Expression Endocrinology, December 1, 1998; 139(12): 5157 - 5163. [Abstract] [Full Text] [PDF]