Biology of Reproduction, Vol 21, 873-882, Copyright © 1979 by Society for the Study of Reproduction

Electropharetic Evidence for the Identity of the Major Zinc-Binding Polypeptides in the Rat Sperm Tail

¹ Department of Human Genetics and Development and Center for Reproductive Sciences, Columbia University, New York, New York 10032

Zinc, an important metallic constituent of mammalian spermatozoa, is incorporated during spermiogenesis into the dense fibers of the sperm tail. To test its relative affinity for sperm structural proteins, ⁶⁵Zn was administered intratesticularly to mature Sprague-Dawley rats and recovered in cauda epididymidal spermatozoa 16-18 days postinjection, when its concentration in these cells was maximal. As expected, the ⁶⁵Zn was localized almost entirely within tail structures stabilized by -S-S-bonds (tail keratin), at least 75% being found within a fraction consisting mainly of dense fibers. After electrophoresis in dodecyl sulfate-polyacrylamide gels, tail keratin or dense fiber fractions labeled by intratesticular injection of [³⁵S]-cysteine showed three peaks of ³⁵S-labeled protein, with apparent molecular weights of 24,000, 15,000 and 11,000. Only the first of these protein components retained substantial amounts of ⁶⁵Zn during co-electrophoresis of ³⁵S and ⁶⁵Zn-labeled fractions. Following carboxymethylation, it was revealed to be heterogeneous, consisting of at least 2 polypeptides, whose unexpectedly low electrophoretic mobilities corresponded to molecular weights of 36,000 and 30,000. Efficient retention of ⁶⁵Zn by its unmodified precursor during electrophoresis required the presence of at least 40 mM dithiothreitol in the applied samples and was achieved equally well whether the ⁶⁵Zn was introduced in vitro or in vivo. Selective binding of ⁶⁵Zn by some, but not all, of the cysteine-rich polypeptides in the sperm tail extracts may be of physiological significance, particularly since those macromolecules that demonstrated the greatest affinity for zinc are believed to be the major constituents of dense fibers.

Note:
ACKNOWLEDGMENTS The author wishes to thank Ms. C. Y. Hsu and Mr. Robert Jurasinski for their excellent technical assistance. This research was supported by NIH Grant No. HD-05316.

This article has been cited by other articles:

				J. Xue, H. A. Tarnasky, D. E. Rancourt, and F. A. van der Hoorn Targeted Disruption of the Testicular SPAG5/Deepest Protein Does Not Affect Spermatogenesis or Fertility Mol. Cell. Biol., April 1, 2002; 22(7): 1993 - 1997. [Abstract] [Full Text] [PDF]

				C. J. Flickinger, J. Rao, L. Ann Bush, N. E. Sherman, R. J. Oko, F. C.L. Jayes, and J. C. Herr Outer Dense Fiber Proteins Are Dominant Postobstruction Autoantigens in Adult Lewis Rats Biol Reprod, May 1, 2001; 64(5): 1451 - 1459. [Abstract] [Full Text]

				C. Petersen, L. Fuzesi, and S. Hoyer-Fender Outer dense fibre proteins from human sperm tail: molecular cloning and expression analyses of two cDNA transcripts encoding proteins of ~70 kDa Mol. Hum. Reprod., July 1, 1999; 5(7): 627 - 635. [Abstract] [Full Text] [PDF]

				H. Brohmann, S. Pinnecke, and S. Hoyer-Fender Identification and Characterization of New cDNAs Encoding Outer Dense Fiber Proteins of Rat Sperm J. Biol. Chem., April 11, 1997; 272(15): 10327 - 10332. [Abstract] [Full Text] [PDF]

				X. Shao, H. A. Tarnasky, U. Schalles, R. Oko, and F. A. van der Hoorn Interactional Cloning of the 84-kDa Major Outer Dense Fiber Protein Odf84. LEUCINE ZIPPERS MEDIATE ASSOCIATIONS OF Odf84 AND Odf27 J. Biol. Chem., March 7, 1997; 272(10): 6105 - 6113. [Abstract] [Full Text] [PDF]