Abstract
Whole histone and histone fractions were extracted from chromatin prepared from the nuclei of an amicronucleate strain GL of Tetrahymena pyriformis during exponential growth. Their chromatographic behaviors on a CM-cellulose column (using our method) and also on Amberlite CG-50 and Bio-Gel P-60 were compared with those of histones of rat liver, rat thymus, and calf thymus. The protozoan histone fractions obtained by Amberlite or Bio-Gel chromatography were rechromatographed on CM-cellulose and eight or nine fractions were separated. Most of these fractions gave single bands with different mobilities on polyacrylamide gel electrophoresis, but they could be grouped into five or six main types of molecular species with different amino acid compositions and molecular sizes corresponding to the five main types of mammalian histones. Similarities and differences between the corresponding protozoan and mammalian types suggest that both conservation and variation of each sequence must have occurred during evolution from a common ancestor to protozoa and to mammals.

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