Studies on histones. 5. The histones of the Crocker sarcoma and spontaneous mammary tumours of mice

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Abstract
Histones were isolated from a spontaneous and a transplanted tumor. The preparations differ mainly in the content of acidic protein impurities. The best preparations were obtained by mild homogenization in a medium containing ethylenediaminetetra-acetate or sodium citrate; 84-88% of the N-terminal groups of these histones was proline or alanine. Chromatography or specific extraction procedures gave a fairly satisfactory lysine-rich fraction (f1) but only partial separation of the slightly lysine-rich (f2) and arginine-rich (f3) fractions. The normal content of arginine-rich fraction is, however, suggested by the normal content of alanine N-terminal groups in the whole histone. These results, together with consideration of electrophoresis patterns and yields, support the suggestion of Hnilica et al. (1962) that any differences between tumor and non-tumor histones are too small to be detected by the methods available.