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

Abstract

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 dodecyl sulfate by electrophoresis on polyacrylamide gels containing the detergent. Among some 20 bands initially resolved, 8 were found labeled, corresponding to MW 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; 3 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.