MOLECULAR IDENTITIES OF HUMAN SPERM PROTEINS THAT BIND HUMAN ZONA-PELLUCIDA - NATURE OF SPERM-ZONA INTERACTION, TYROSINE KINASE-ACTIVITY, AND INVOLVEMENT OF FA-1

The present study was conducted to investigate the molecular identitie s, nature of interaction, and tyrosine phosphorylation activity of the sperm-zona pellucida binding proteins in humans. Sperm proteins belon ging to four major molecular regions, namely 95, 63, 51, and 14-18 kDa , reacted with zona pellucida proteins in the Western blot and immunop recipitation procedures. In these procedures, zona pellucida protein t hat reacted strongest with the sperm proteins belonged to the molecula r region of 55 kDa (ZP3), besides weakly reacting proteins in the 110- kDa (ZP1/ZP2) and 14-18-kDa molecular regions. The major forces involv ed in the sperm-zona protein interactions were of hydrophobic and ioni c in nature. Three (95, 51, and 14-18 kDa) of the four molecular regio ns of sperm proteins that bound to the zona pellucida proteins also se em to involve o-phospho-L-tyrosine residues in their interaction, and these proteins demonstrated the presence of phosphotyrosine residues, and the 51-kDa protein also showed autophosphorylating activity in the in vitro kinase assay. The sperm binding zona protein of 55 kDa also demonstrated autophosphorylating activity. Using specific monoclonal a ntibody to the well characterized sperm-specific glycoprotein, designa ted FA-1, and the competitive inhibition in the immunoprecipitation pr ocedure, it was found that the 51 kDa protein is indeed FA-1 antigen. Besides elucidating the molecular nature of the sperm-zona interaction , these antigens will find application in the development of a multiva lent contraceptive vaccine, and may also help in specific diagnosis an d treatment of infertility mediated through defective gamete (sperm or oocyte) function. (C) 1994 Wiley-Liss, Inc.