An immunological comparison of rye and calf histones.

The rye and calf histones were fractionated by differential solubility and exclusion chromatography. Antibodies were produced against histones H1, H2A, H2B, and H3 of both species and the extent of cross-reaction was measured by microcomplement fixation. The results allowed the identification of rye histones H2A and H2B. The near structural identity of the H3 histones was confirmed by the small immunological distance which indicated an amino acid difference of less than 2% between rye and calf. The interspecific differences found for both H2A and H2B were greater, the amino acid difference estimated from the immunological distance being between 10 and 20%. H1 gave no immunological cross-reaction, indicating a large (greater than 40%) difference in the structure of this protein in the two species. The extent of variation that a histone fraction shows between plant and animal species is probably related to its role in chromatin organization.