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Journal of Andrology, Vol 3, Issue 5 289-296, Copyright © 1982 by The American Society of Andrology

Human and Ram Seminal Plasma Both Contain a Calcium-Dependent Regulator Protein

Calsemin

MARK P. BRADLEY 1 AND IAN T. FORRESTER 1

1 Calcium and Reproductive Biology Laboratory, Department of Biochemistry, University of Otago, Dunedin, New Zealand

Biochemical aspects of post-testicular sperm maturation have been studied. Partial purification of either human or ram seminal plasma yields a heat-stable, acidic protein which is a Ca2+-dependent regulator of 3':5'-cyclic nucleotide phosphodiesterase. This protein fraction has been provisionally named calsemin. Human calsemin activates the flagellar plasma membrane Ca2+-ATPase of ram epididymal and ejaculated spermatozoa by 290% and 20%, respectively. Activation is abolished by trifluoperazine. The addition of calsemin plus Ca2+ to isolated ram caudal spermatozoa results in a three-fold stimulation of flagellar beat activity. These results lead us to propose that only after interaction between calsemin and the sperm flagellar plasma membrane can the Ca2+-ATPase obtain full expression to maximise Ca2+ efflux from the flagellum and thereby cause a stimulation and coordination of sperm flagellar beat activity. This finding may provide a partial biochemical explanation for the development of mammalian sperm motility.

     Key words: Spermatozoa, initiation of motility, Ca2+-dependent regulator, Ca2+-ATPase, epididymis, seminal plasma

Submitted on August 12, 1981
Revised on November 23, 1981
Accepted on December 3, 1981






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Copyright © 1982 by The American Society of Andrology.