Isolation of a calcium-binding protein of the acrosomal membrane of bovine spermatozoa.

The mammalian sperm acrosome reaction is a calcium-dependent exocytotic event characterized by extensive fusion between the plasma and the outer acrosomal membrane. The mechanisms by which elevation of cytosolic calcium initiates the membrane fusion process are not understood and the present study was undertaken to identify calcium-binding proteins in the acrosomal membrane (AM) of bovine spermatozoa. Sperm heads, purified from sonicated spermatozoa, were used to isolate an acrosomal membrane-enriched fraction on Percoll density gradients.