Purification and Properties of S-100 Protein from Porcine Brain*

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Abstract
Porcine brain S-100 proteins were purified by ammonium sulfate fractionation and column chromatography on DEAE-cellulose and Sephadex G-75, and two major S-100-fractions, Fractions 3-2-3 and 4-2-3, were obtained. The amino acid compositions of these fractions were quite different from each other. Upon polyacrylamide gel elec-trophoresis, Fraction 4-2-3 was found to be homogeneous in both 7.5% and 14% gels. On the other hand, Fraction 3-2-3 was homogeneous in 7.5% gel, but showed heterogeneity in 14% gel. This heterogeneity did not disappear after treatment with β-mercaptoethanol. The presence of calcium ions affects the electrophoretic behavior of Fraction 3-2-3, but not that of Fraction 4-2-3. Both fractions, however, possessed a molecular weight of 26,000 as determined by gel nitration on Sephadex G-100. When gel electrophoresis was performed in 0.1% sodium dodecyl sulfate in 12.5% gel, Fraction 4-2-3 gave a single band of MW about 19,000, whereas Fraction 3-2-S gave two bands of MW about 19,000 and 7,000. These results indicate that porcine brain contains several S-100 protein components and that at least some of them are composed of subunits. The results of peptide mapping and N-terminal analysis of Fraction 3-2-3 suggest that this fraction may be a mixture of similar S-100 proteins.

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