Changes in surface protein structure of bull spermatozoa during epididymal maturation

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Abstract
The surface proteins of bull spermatozoa from caput and cauda epididymidis were labeled by lactoperoxidase-catalyzed radioiodination and solubilized and analyzed by sodium dodecyl sulfate-polyacrylamide gel-electrophoresis. The surface protein patterns of caput and cauda epididymal spermatozoa resembled each other but some distinct differences could be found. Caput epididymal spermatozoa revealed a protein peak with MW of 15,000-18,000 daltons but this peak was not found on cauda epididymal spermatozoa. On caput epididymal spermatozoa the most intensely labeled protein peak was located between 90,000 and 100,000 daltons but on cauda epididymal spermatozoa the corresponding peak was only weakly labeled and had a MW of 80,000-90,000 daltons. Surface protein with MW of 42,000-47,000 daltons was dominating on cauda epididymal spermatozoa. The surface protein structure of cytoplasmic droplets did not drastically differ from that of epididymal spermatozoa.