CHARACTERIZATION OF 2 ANTIGENICALLY RELATED INTEGRAL MEMBRANE-PROTEINS OF THE GUINEA-PIG SPERM PERIACROSOMAL PLASMA-MEMBRANE

The periacrosomal plasma membrane of mammalian spermatozoa functions b oth in recognition and in binding of the egg's zona pellucida and in t he acrosome reaction. This study characterizes two antigenically relat ed proteins with molecular weights of 35 kD (PM35) and 52 kD (PM52) of the guinea pig sperm periacrosomal plasma membrane. Polyclonal antise ra were prepared against electrophoretically purified PM35 or PM52. Ea ch antiserum recognized both the 35-kD and 52-kD polypeptides on Weste rn blots, indicating that they are structurally related. This conclusi on was supported by peptide mapping experiments demonstrating comparab ly sized fragments of both PM35 and PM52. Both PM35 and PM52 behave as integral membrane proteins during phase-separation analysis with Trit on X-114. Electron microscopic immunocytochemistry and differential fr actionation of sperm membranes established that both PM35 and PM52 are exclusively localized to the periacrosomal plasma membrane. Three dif ferent antisera were used for ultrastructural studies, and each specif ically bound the cytoplasmic but not the extracellular membrane surfac e. The electrophoretic mobilities of the PM35 and PM52 polypeptides we re unchanged during sperm maturation and during the ionophore-induced acrosome reaction. The localization of PM35 and PM52 suggests a potent ial role for these integral plasma membrane proteins in signal transdu ction or membrane fusion events of the acrosome reaction. (C) 1994 Wil ey-Liss, Inc.