Purification and characterization of a sperm motility inhibitor in human seminal plasma

A sperm motility inhibitor from human seminal plasma was purified and characterized. The purification procedure includes dialysis, ion exchange chromatography on SP-Sephadex C-25 and adsorption chromatography on hydroxylapatite. With this procedure, the seminal plasma motility inhibitor was purified 290-fold with a 24% recovery in inhibitory activity. Its molecular weight has been estimated at 18,000 to 22,000 by sodium dodecyl sulfate polyacrylamide gel electrophoresis, but at 13,000 to 15,000 according to molecular sieving under native conditions. The mobility inhibitor has an isoelectric point pH 9.1. It is stable over a wide range of pH (5 to 10) and at temperatures up to 60 C. The observation that the seminal plasma factor inhibited purified bull dynein ATPase in a concentration-dependent manner may suggest that it blocks the motility of demembranated spermatozoa by interfering with dynein arm function.