Glycosylated Human Prolactin

A glycosylated form of human PRL (G-hPRL) was isolated from pituitary glands. The glycoprotein was separated from the major form of PRL on columns of lentil lectin-Sepharose 4B. The major form of PRL did not bind to the lentil lectin, whereas the glycosylated modification did and could be eluted with methyl-α-D-mannopyranoside. By gel electrophoresis in sodium dodecyl sulfate, a mol wt of 25,000 was estimated for the glycosylated PRL. The mol wt of hPRL is 23,000. In a RIA for hPRL, the glycosylated hormone was about one third as reactive as the principal form. Since there is only one Asn-X-Ser(Thr) sequence in hPRL, the asparagine at position 31 is the likely point of N-linked glycosylation. (Endocrinology 116: 359–363, 1985)