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Isolation and partial characterization of rat sperm tail fibrous sheath proteins and comparison with rabbit and human spermatozoa using a polyclonal antiserum

Rat sperm tail fibrous sheath was isolated using mechanical and chemical dissection methods from spermatozoa collected from the cauda epididymis. The procedures used to isolate the fibrous sheath were monitored by phase-contrast microscopy and purity was verified by electron microscopy. SDS-PAGE of isolated total fibrous sheath revealed at least 17 bands when stained with Coomassie brilliant blue and 20 bands with silver stain. The most intensely staining proteins, using both staining methods, were a double band at 80–87 kDa, and a band at 28.5 kDa, whereas with silver staining, bands at 66.2 kDa and 32.7 kDa were also intensely stained. Electroelution following SDS-PAGE was used to isolate 11 of these proteins (116.4, 87.5, 80.9, 66.2, 57.2, 49.7, 46.8, 37.3, 32.7, 28.5 and 15.5 kDa). Amino acid analysis revealed that these proteins were abundant in aspartic and glutamic acid, glycine, serine and leucine, while histidine and phenylalanine were of low abundance. The content of cystine varied widely from 9.4% to 1.4%. The amino termini of the 80.9 kDa, 32.7 kDa, 28.5 kDa and 15.5 kDa proteins were blocked. Immunofluorescence microscopy demonstrated that a polyclonal antiserum to isolated rat fibrous sheath was localized to the principal piece of the rat, rabbit and human spermatozoa, but in the rabbit it also labelled the equatorial region of the head. Western blotting detected all protein bands in isolated fibrous sheath and a similar range of proteins in the spermatozoa of rat and rabbit. Human sperm proteins of 116 kDa and 80 kDa were immunoreactive in common with other species, and there was only weak crossreactivity with the other proteins. These data suggest the presence of common epitopes in the proteins of all three species.