The long term goals of this research project are to define both chemically and biologically a set of sperm molecules which are necessary for one or more steps in the fertilization process. During the current grant period emphasis has been placed on defining the biological function of the rabbit sperm membrane autoantigen, RSA, as a zona pellucida binding protein and on obtaining CDNA clones which would allow further characterization of sperm autoantigenic sites and zona binding proteins. To continue this line of investigation, this revised renewal application will focus on four sperm molecules selected for study at the molecular level with regard to their role in fertilization and zona binding. Using the cyclic model as a working hypothesis, which was developed during the current grant period and which is explained in detail in Section C.4.(b).1-4, this proposal will specifically investigate the mechanism by which spermatoza attach to and penetrate (degrade) the zona pellucida. An understanding of the mechanism of sperm-zona interaction would allow precise targets for both infertility diagnosis and contraception. Therefore, this proposal's specific aims are: I. The mechanism of action of three sperm molecules on binding to and interacting with (degrading or releasing) the zona pellucida. I.1) The molecular characterization of the rabbit sperm membrane autoantigen, RSA, with regard to the amino acid sequences which specifically bind zona pellucida. I.2) The molecular characterization of the role of the sperm enzyme acrosin in zona binding. 3) The molecular characterization of the role of the sperm enzyme arylsulfatase A in zona binding. II. The isolation and biological characterization of a newly discovered sperm nuclear autoantigenic protein (NASP), with regard to: (A) biological function and (B) the amino acid sequences of autoantibody binding sites. Molecular sites methodology will be used to characterize specific sequences.