Purification of ovine placental lactogen (oPL) using high-performance liquid chromatography. Evidence for two forms of oPL.
After initial purification of ovine placental lactogen (oPL) using the procedures described previously [(1976) Endocrinology 98, 65-75], the oPL preparation was further purified by high-performance liquid chromatography (HPLC) using an anionic exchange column (Bio-Sil TSK DEAE-2-SW). Two forms of oPL with different relative mobilities on HPLC were isolated and designated oPL-I and oPL-II. Subsequent analysis by polyacrylamide gel electrophoresis containing SDS revealed that oPL-I and oPL-II are nearly homogeneous (greater than 90% pure) and are identical in apparent Mr (approx. 22 000-23 000). Like human growth hormone (hGH), oPL-I and oPL-II are equally active in the radioreceptor assays for growth hormone-like activity (RRA-GH) and for prolactin-like activity (RRA-RRL). In the radioimmunoassay of oPL, both oPL-I and oPL-II are immunologically similar. Analysis of amino acid composition revealed that oPL-I and oPL-II consist of 199 and 196 residues, respectively, and have almost identical residues except that oPL-I has a higher content of glycine. Furthermore, both oPLs have a general similarity in amino acid composition to oGH and oPRL except for a lower content of methionine and leucine but with a higher content of lysine. Our studies demonstrated the presence of two similar forms of oPL. Whether these two similar forms of oPL share identical primary structure remains to be determined.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001667:Binding, Competitive; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005260:Female; D013006:Growth Hormone / Q000378:metabolism; D007700:Kinetics; D010920:Placenta; D010928:Placental Lactogen / Q000302:isolation & purification* / Q000494:pharmacology; D011247:Pregnancy; D011388:Prolactin / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D011981:Receptors, Prolactin; D011986:Receptors, Somatotropin; D012756:Sheep
D000596:Amino Acids; D011956:Receptors, Cell Surface; D011981:Receptors, Prolactin; D011986:Receptors, Somatotropin; D011388:Prolactin; D013006:Growth Hormone; D010928:Placental Lactogen