PURIFICATION OF EGIP-D-BINDING PROTEIN FROM THE EMBRYOS OF THE SEA-URCHIN ANTHOCIDARIS-CRASSISPINA

Exogastrula-inducing peptides (EGIPs) are intrinsic factors that are p resent in eggs and embryos of the sea urchin Anthocidaris crassispina. They induce exogastrulation when added exogenously to the embryos. In the present study, we isolated an EGIP-D-binding protein (EBP) from a homogenate of mesenchyme blastulae: EBP had an apparent molecular wei ght of 33,000. The N-terminal amino acid sequence of EBP had a sequenc e homology to HLC-32 and bep4 identified in other sea urchin embryos. In addition to its ability of binding to EGIP-D, EBP also inhibited ex ogastrulation induced by EGIP-D. These results suggest that EBP plays an essential role in EGIP-D-induced exogastrulation.