Characterization of a novel prolactin-related protein from bovine fetal placenta

The bovine fetal placenta transcribes a family of PRL-related genes that are distinct from the bovine placental lactogen gene. To demonstrate that one of these cDNAs, bovine PRL-related cDNA-I (bPRCI), is expressed at the protein level, a recombinant form of the bPRCI product was overexpressed in Escherichia coli. An antiserum raised against this recombinant product did not cross-react with the pituitary members of the PRL-GH family or with bovine placental lactogen, although cross-reactivity within the bPRC subfamily cannot be ruled out. The antiserum detected a doublet with apparent mol wt of 34,000 and 35,000 in bovine fetal placenta, but not in other fetal tissues. Treatment with several glycosidases revealed a glycoprotein with asparagine-linked carbohydrates of the biantennary complex or hybrid type. We conclude that the bovine fetal placenta expresses at least one of the novel members of this gene family at the protein level.