Improved fractionations of arginine-rich histones from calf thymus

Abstract

Calf-thymus histones, chromatographed on carboxymethylcellulose, gave two very lysine-rich fractions with sodium acetate-sodium chloride elution, a slightly lysine-rich histone with 0-01 [image]-hydrochloric acid elution and finally an arginine-rich histone (f3), eluted with 0-02[image]-hydrochloric acid. Material with very similar amino acid analysis and chromatographic properties to fraction f3 above could be readily prepared in bulk by extraction of the tissue with ethanol-hydrochloric acid and subsequent dialysis of the extract against ethanol. The arginine-rich histone, which was precipitated, had 1 mole of N-terminal groups/18 000 weight, which in reprecipitated material was almost entirely alanine. The chief C-terminal group detected by carboxypeptidase and on hydrazinolysis was also alanine, but the yield was only about one-half that of the N-terminal group. When lower concentrations of ethanol were used in the extraction the N-terminal groups of the final precipitates became more complex. Extraction of washed tissue with successively lower concentrations of ethanol showed that the arginine-rich histones were extracted at higher, and the lysine-rich histones at lower ethanol concentrations. In all cases the solvent used was 0.25[image] with respect to hydrochloric acid. Starch-gel electrophoresis, column chromatography and perhaps the C-terminal group analyses indicated that the arginine-rich material with virtually a single N-terminal group still consisted of several components.