Identification of bovine trophoblast protein-1, a secretory protein immunologically related to ovine trophoblast protein-1

Publisher Website
Google Scholar
Abstract
Summary. This paper demonstrates that a group of proteins, representing a major secretory component of cattle conceptuses, is immunologically related to ovine trophoblast protein-1 (oTP-1), a principal product of culture Day 13 to 21 sheep conceptuses. Conceptuses from cows (Day 17–18) and ewes (Day 16–17) were cultured for 24 h in the presence of l-|3H]leucine. By using a rabbit antiserum to oTP-1 and Ouchterlony double-immunodiffusion analysis it was shown that material in the bovine conceptus culture medium was serologically related, but not identical, to oTP-1. A solid-phase radiobinding assay indicated that the cross-reacting bovine secretory component had an affinity for anti-oTP-1 antibody similar to that of oTP-1. Anti-oTP-1 antiserum specifically immunoprecipitated a group of 6–8 polypeptides from culture medium of cow conceptuses which, when analysed by two-dimensional gel electrophoresis, fell into two major molecular weight classes (22 000 and 24 000) with isoelectric points between 6·5 and 6·7. These immunoprecipitated polypeptides, defined as bTP-1, constituted the major secretory products of Day 16–25 cow conceptuses. They were larger and more basic than oTP-1 polypeptides (Mr about 18 000; pI 5·4–5·7). Anti-oTP-1 antiserum also recognized the major translation product of Day 17 bovine conceptus mRNA, a polypeptide significantly smaller (Mr ∼ 18 000) than the secreted protein. It is suggested that oTP-1 and the homologous bovine protein may play similar roles in the phenomenon of maternal recognition of pregnancy in the two species.