The objective of this study is to provide a comprehensive evaluation of polypeptides exposed to the hydrophilic (peripheral proteins) or hydrophobic (integral proteins) region of the plasma membrane of rat testicular and epididymal spermatozoa. This will be done by reacting intact spermatozoa recovered from rete testis fluid and different regions of the epididymis with permeable, semi-permeable, or nonpermeable, radioactive chemical crosslinking reagents that are photosensitive. Following photolysis the plasma membrane will be purified by density gradient centrifugation, and the proteins will be analyzed by polyacrylamide gel electrophoresis and autoradiography. In other studies, nearest neighbor analysis of selected epididymal secreted proteins will be carried out. By identifying the major polypeptides that comprise the integral and peripheral proteins of the sperm plasma membrane as a function of epididymal transit, these studies may provide the groundwork for future investigations to test the functional significance of proteins that are added to, or removed from the sperm plasma membrane during development. The function of surface proteins during fertilization also represents an important direction for further research. Finally, these results may prove important to our understanding of the role secreted proteins play in the reproductive process.
