A protein, present in bovine seminal plasma, initiates forward motility in immature, immotile caput spermatozoa that have been incubated with a cyclic AMP phosphodiesterase inhibitor. An improved motility assay was developed to study this process and the protein involved. This forward motility protein exhibits multiple forms when fractionated on the basis of charge or molecular weight. Molecular sieving in urea or sodium dodecyl sulfate and dithiothreitol results in a single peak of activity which will re-form the larger aggregates in the absence of these agents. The molecular weight of this monomeric motility protein, as estimated from molecular sieving under these dissociating conditions, is 37,500. The forward motility protein can be partially purified by heat treatment, gell chromatography in urea, and affinity chromatography on concanavalin A/agarose. Enzymatic treatments further suggest a glycoprotein nature, i.e. treatment with beta-galactosidase, neuraminidase, alpha-mannosidase, or galactose oxidase reduces its activity by 50%; treatment with trypsin completely abolishes forward motility protein activity. On the basis of concurrent studies on the activity, properties, and distribution of forward motility protein in bovine body fluids, it is suggested that this protein is involved in the development of the capacity for motility as sperm traverse the epididymis.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1978

Evidence for an epididymal origin of bovine sperm forward motility protein.

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Animals↗

PubMed1978

Initiation of sperm motility in the mammalian epididymis.

Spermatozoa acquire the capacity for motility as they traverse the mammalian epididymis. The biochemical basis for this induction of motility is still largely unknown. Current theories are discussed and recent studies from the authors' laboratory are described which indicate that two separate processes are involved and that these act synergistically. These processes are an increase in the intrasperm content of cyclic AMP during epididymal transit combined with the binding of a specific forward-motility protein. A second increase in cyclic AMP and stimulation by calcium ion is likely involved in the expression of the acquired potential for motility at the time of ejaculation.

Adenosine Triphosphatases↗