Fig. 9. A 64 kDa polypeptide is detected in human ejaculate by anti-Mytilus MAP and anti-Drosophila esterase S antibodies. Equal amounts (20 µg of total protein) of cell-free (Lane 1) and sperm-cell (Lane 2) fractions of human semen were separated by SDS-PAGE (A), blotted on membranes and treated with anti-MAP (B) or anti-esterase S (C) antibodies. Lane 3, rabbit liver carboxylesterase, 1 µg (Sigma). Note that the intensity of immunostaining of the 64 kDa band is slightly higher in the sperm than in the seminal fluid. The positions of marker proteins (kDa) are shown.