A 23 kDa protein from rat sperm plasma membranes shows sequence similarity and phospholipid binding properties to a bovine brain cytosolic protein.

A 23 kDa protein that is a major component of rat epididymal secretions and sperm plasma membranes has been purified and partially sequenced. A data-base search revealed approximately 85% sequence similarity with a phosphatidyl-ethanolamine-binding protein from bovine brain cytosol. The rat 23 kDa protein also showed selective affinity for phosphatidylethanolamine (Kd = 1.6 x 10(-5) M) with lower activity towards phosphatidylinositol and phosphatidylcholine. It is suggested that differential affinity of protein antigens towards asymmetrically aligned phospholipids in sperm plasma membranes could account for their organisation into specific regional domains.