BIOCHEMISTRY OF SPERM-EGG INTERACTION AND FERTILIZATION

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The long-term objective of this research program is to gain a detailed biochemical knowledge of the process of animal fertilization. This proposals describes basic research that will increase our knowledge of processes underlying sperm-egg interaction during fertilization. This knowledge is essential to the future development of non-hormonal methods of contraception in higher forms such as man. Sea urchins are used in this work because they are the only group of animals producing enough sperm nd eggs to permit biochemical studies. What little we do know about mammalian fertilization shows that striking similarities exist between mammals and sea urchins thus making the work on sea urchins relevant to mammals. The sea urchin is the paradigm for fertilization research just as the mouse is for cancer research. The specific aims of this program are: to characterize and determine the function of three sperm membrane proteins which we call 84K, 110K & 115K. We believe 84K is involved in triggering the sperm acrosome necessary for binding the sperm to the egg. The 110K & 115K together comprise 50% of the sperm membrane protein, so they must be very important to the sperm function. We can isolate the sperm membrane in the form of vesicles (SMV) which we will characterize fully and also study their interaction with eggs. We will determine if methylation and phosphorylation of sperm lipids and proteins occurs during the acrosome reaction. We will isolate and characterize the sperm surface antigenic component common to all animal sperm we have tested. This may have the potential of being an ideal immunocontraceptive. We will study the sperm binding protein, bindin, in greater detail and determine the amino acid sequence of two bindins and also study its carbohydrate binding specificity. We will study the mechanism by which extracellular calcium activates the adenylate cyclase of abalone sperm, and the mechanism by which sea urchin eggs redistribute bindin-containing vesicles on their surfaces. We will determine the role of the corticsal granule glucanase in fertilization and also identify specific phosphoproteins regulating the metabolic state of the egg before, during and after fertilization. Lastly, we will study the biochemistry of the calcium-mediated explosion of isolated egg cortical granuels. The success of this project will greatly increase our knowledge of sperm-egg interaction.