High-sulphur proteins from alpha-keratins. II. Isolation and partial characterization of purified components from...

The present paper continues the study of the reduced and S-carboxymethylated high-sulphur proteins from mouse hair. Fractions have been obtained in a substantially purified form by fractional precipitation with ammonium sulphate at pH 6, followed by ion exchange chromatography on cellulose phosphate at pH 2.6. Approximately 80% by weight of the high-sulphur proteins fall into the ultra-high-sulphur category (carboxymethylcysteine content greater than 26 residues per 100 residues), and they cover a molecular weight range of 17000-28000. The components show a remarkable diversity in amino acid composition; for example the contents of arginine and glycine each vary by about 3:1. The remainder of the proteins contain 17-20 residues per 100 residues of carboxymethylcysteine, are smaller in size (molecular weight 11500), and also show great diversity in overall amino acid composition. Molecular weights were determined by chromatography on controlled-pore glass and confirmed by gel filtration on Sephadex G-100 and Sepharose 6B. A comparison of the results suggests that the values obtained should be reliable to within 10%.