A low molecular weight endometrial secretory protein which is increased by ovine trophoblast protein-1 is a beta...

Ovine trophoblast protein-1 (oTP-1), stimulates the secretion of several proteins in explant culture of day-12 cyclic ovine endometrium. We partially purified and identified one of these proteins, an 11,000 Mr, pI approx. 6 protein by N-terminal amino acid sequencing and immunoprecipitation using antibody to human beta 2-microglobulin. The protein was purified from cultures of endometrium collected from day-16 pregnant ewes. The N-terminal amino acid sequence was 40-55% homologous to beta 2-microglobulin from a variety of species. Antibody to human beta 2-microglobulin immunoprecipitated the protein and another protein of similar molecular weight but more acidic pI. Using immunoprecipitation of radiolabelled proteins from culture, we demonstrated that oTP-1 increased production of this protein by 40% (P less than 0.05). We conclude that oTP-1 increases the secretion of a beta 2-microglobulin-like protein from day-12 non-pregnant endometrium in culture.