Glycosylation of ovine prolactin during cell-free biosynthesis.
Recently, a glycosylated form of ovine PRL (oPRL) was isolated from a crude pituitary preparation. As glycosylation of PRL was unexpected and because the composition of the oligosaccharide-containing peptide indicated the carbohydrate portion to be extensively degraded, studies of the glycosylation of oPRL during cell-free biosynthesis were initiated. Two glycosylated forms of oPRL can be recognized when biosynthesis occurs in ovine pituitary microsomes. Both forms are converted to mature PRL by digestion with endoglycosidase H and, thus, appear to contain only asparagine-linked, high mannose-type carbohydrate moieties. In contrast, immunoprecipitates from bovine pituitary microsomes consist of the expected (and nonglycosylated) pre-PRL and PRL. The results are consistent with the absence of a sequence segment in the bovine hormone which permits glycosylation (Asn-X-Ser- or Thr-) and the presence of the segment Asn31-Leu-Ser- in the ovine hormone. The occurrence of two glycosylated forms of oPRL is not understood; it may result from an additional site in oPRL capable of glycosylation.
D000818:Animals; D050260:Carbohydrate Metabolism; D002417:Cattle; D002474:Cell-Free System; D008861:Microsomes / Q000378:metabolism; D008970:Molecular Weight; D010902:Pituitary Gland / Q000648:ultrastructure; D011388:Prolactin / Q000096:biosynthesis / Q000378:metabolism*; D012756:Sheep
D011388:Prolactin