Evidence that selenium in rat sperm is associated with a cysteine‐rich structural protein of the mitochondrial capsules

Abstract

Abstract The keratinous capsules surrounding rat sperm mitochondria were isolated 24 days after intratesticular injections of [ 75 Se] selenite or [ 35 S] cysteine. Dodecyl sulfate‐polyacrylamide gel electrophoresis of purified, doubly labeled mitochondrial capsules revealed only a single 75 Se‐labeled component, whose molecular weight was 17,000, in agreement with previously reported observations obtained with cruder sperm fractions. Most of the 35 S label and the major zone of stained protein on the gels coincided with the position of 75 Se, suggesting that selenium is associated with a cysteine‐rich structural protein. The level of selenium in rat sperm, 195 ± 3.2 ng/10 8 sperm (approximately 30 ppm), determined by hydride generation and atomic absorption spectrophotometry, is consistent with a structural function for this trace element in the sperm.