| Abstract: | Plasma membranes isolated from the flagella of ram ejaculated sperm were found to contain a Ca2+ + Mg2+]-ATPase. Freeze-fracture electron microscopy showed the membranes occur as vesicles. The membrane vesicles actively accumulate Ca2+, uptake was reversed by the ionophore A23187 and inhibited by either ruthenium red or La3+. The plasma membranes contain two major proteins, designated proteins A and B, with molecular weights of 109,000 and 18,300 daltons, respectively. Protein B is not detected in plasma membranes isolated from ram epididymal sperm. The plasma membrane Ca2+ pump may be modulated by protein factors present in seminal plasma. |
