Characterization of the postacrosomal sheath of bovine spermatozoa

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Abstract
A purified head fraction was prepared from bovine epididymal spermatozoa and was utilized to identify the solubility characteristics and major polypeptide components of the postacrosomal sheath. Sperm heads extracted in nonionic‐detergent‐containing or high‐salt‐containing solutions retained an intact postacrosomal sheath, but it was readily solubilized by high pH extraction solutions. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis revealed a major polypeptide of 58,000 daltons (58‐kD) in the high pH extract solution. Antibodies to the 58‐kD polypeptide specifically reacted with the postacrosomal segment by immunofluorescence and by electron microscopic immunohistochemistry were shown to bind the postacrosomal sheath. We conclude that this 58‐kD polypeptide is a constituent of the postacrosomal sheath and that its distribution is restricted to the postacrosomal segment.