The structure and function of caltrin (calcium transport inhibitor) proteins from seminal fluids will be studied. The proteins will be purified from seminal vesicle secretions or seminal plasma of the hamster, mouse, rat, sheep, and stallion, and the presence of cysteine and carbohydrates will be determined. Pure caltrins will be sequenced. Polyclonal antibodies will be prepared in rabbits and used to localize the specific sites of interaction of caltrins on the sperm surface, as well as to detect the presence of caltrin receptors on the cells. The effect of caltrin proteins on the onset and evolution of the acrosome reaction and the hyperactivated motility of the spermatozoa will be analyzed in vitro. The transition of caltrin from calcium transport inhibitor to enhancer of Ca2+ uptake by the spermatozoa will be studied by chemical and/or enzymatic modification of the structure of the protein. The studies will include partial and total deglycosylation and cysteine modification. Histologic studies by immuno-electron microscopy will be designed to determine the type of cells responsible for caltrin synthesis in the seminal vesicle tissue. The existence of caltrin- precursor proteins will be analyzed using immuno-biochemical approaches. Purified caltrins will be used in X-ray crystallographic studies.
