Biology of Reproduction, Vol 24, 617-626, Copyright © 1981 by Society for the Study of Reproduction

Surface Proteins and Glycoproteins of Ejaculated Bovine Spermatozoa. I. Iodination and Proteolytic Digestion

¹ Department of Biochemistry, University of Wyoming, Laramie, Wyoming 82071

Proteins exposed on the external surface of the bovine sperm membrane were identified by ¹²⁵I-iodination catalyzed by lactoperoxidase and proteolytic digestion by trypsin and chymotrypsin. The surface-labeled proteins were analyzed after solubilization in sodium dodecylsulfate by electrophoresis on polyacrylamide gels containing the detergent. Among some 20 bands initially resolved, eight were found labeled, corresponding to molecular weights of approximately 155,000, 126,000, 93,000, 75,000, 53,000, 29,000, 26,000, and 15,000. Evidence is presented that these polypeptide bands were not contaminants from the seminal fluid. Two bands of 26,000 and 15,000 were resistant to digestion by trypsin at the surface, whereas three bands of 29,000, 26,000, and 15,000 were insensitive to chymotrypsin. The rest of the bands were sensitive to both trypsin and chymotrypsin.

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ACKNOWLEDGMENTS This work was supported by Grant A-3651, the National Research Council of Canada (B.Y.Y.) and Grant GM 23586 from NIH (USA) (T.H.J.).