Interferon-like sequence of ovine trophoblast protein secreted by embryonic trophectoderm

In most species the length of a pregnancy exceeds that of the luteal phase of the ovarian cycle. The conceptus within the uterus, therefore, is believed to produce a substance or substances which directly or indirectly prolong the lifespan of the corpus luteum and prevent a return to ovarian cyclicity. This phenomenon is known as maternal recognition of pregnancy1. The active substance implicated in signalling maternal recognition of pregnancy in the sheep is an embryonic secretory protein, known as ovine trophoblast protein-1 (oTP-1) (refs 2–4), which is targeted in a paracrine manner to the uterine epithelium of the mother5. We report here the primary amino-acid sequence of oTP-1 as inferred from a cloned complementary DNA and demonstrate that the protein is most probably an interferon-alpha.