Calmodulin-like protein in buffalo (Bubalus bubalis) seminal plasma and its effect on sperm Ca++, Mg++-ATPase

A calmodulin-like protein (CLP) has been identified in buffalo (Bubalus bubalis) seminal plasma and partially characterized. It was heat stable and had properties similar to those of the calcium-binding protein, calmodulin. It is present in relatively high concentrations in buffalo seminal plasma. When added to buffalo red-blood cell plasma membrane (RBC ghosts) it increased Ca++, Mg++-ATPase activity by 112%. The activation is counteracted by chlorpromazine and trifluoperazine, the anti-calmodulin drugs. A similar calmodulin-activated Ca++ pump has been found predominantly in the tail fractions of buffalo spermatozoa. The existence of CLP in buffalo seminal plasma may be responsible for some of the physiological changes observed during capacitation and acrosome reaction. A hypothesis has been proposed involving CLP in regulation of these events.