Isolation and characterization of the histone variants in chicken erythrocytes.

Chicken erythrocyte histones 2A, 2B, and 3 can be resolved into nonallelic primary structure variants by polyacrylamide gel electrophoresis in the presence of Triton X-100. These variants were isolated and characterized by analysis of their tryptic and thermolytic peptides. The major variants of chicken H2A and H2B differ from the analogous component of calf thymus by a small number of conservative amino acid substitutions in the basic terminal regions, which interact with DNA. This moderate rate of allelic evolution of the slightly lysine-rich histones contrasts with the complete conservatism found in the arginine-rich histones. Chicken H4 and both chicken H3 variants are identical with their corresponding components in mammals. The amino acid substitutions distinguishing histone variants are located within the highly conserved hydrophobic regions, which are involved in histone--histone interactions.