Purification of S-100a0 protein from rat kidney.

In order to corroborate our previous finding that kidney may contain a considerable amount of S-100-like antigen, concentrations of S-100a0, S-100a and S-100b antigens in rat kidney were determined by an enzyme immunoassay system, which can quantify these 3 forms of S-100 protein separately. It was revealed that rat kidney was rich in S-100a0 antigen, while it was the least occurring form in brain. To confirm the above results, S-100-like antigen in rat kidney was purified, and its physicochemical properties were compared with those of S-100 proteins of bovine brain. Electrophoretic mobility, calcium binding ability, apparent molecular weight, amino acid composition as well as elution profiles from butyl-Sepharose and anion exchange columns were similar to those of S-100a0 protein of bovine brain. These results indicate that S-100a0 protein is not a protein unique to brain, as had long been believed.