Bovine keratohyalin: anatomical, histochemical, ultrastructural, immunologic, and biochemical studies.
Salt extraction studies showed that keratohyalin (KH) could be solubilized and extracted from fresh bovine hoof epidermis. The solubility of KH varied in relation to the molarity of the salt solution used for extraction. Using this information, the extracted KH was aggregated in vitro by dialyzing the high salt extract against distilled water. Histochemical, ultrastructural, and immunologic studies of the resultant particles or macroaggregates showed that the latter had the same properties and immunogenicity as the KH granule in situ and produced antibodies against it. Fractionation of the macroaggregates by polyacrylamide gel electrophoresis demonstrated that the macroaggregates were compsed of sets of 20 polymers whose subunits or monomers had a molecular weight of 16,900. Amino acid analyses showed that the macroaggregates and the various fractionated polymers were similar and that the protein ahd 116 amino acid residues. Serine, arginine, glycine, glutamic acid, and histidine constituted 78% of all residues, and serine alone represented 27%. The molecular weight by amino acid analyses was 16,150 after correction for the 8% ribonucleic acid which appears to be complexed to the protein.