Qualitative Species Differences and Quantitative Tissue Differences in the Distribution of Lysine-rich Histones

Abstract

Species-specific differences in the distribution of lysinerich histones were investigated in spleen tissue of three mammalian (calf, cat, and rat) and one avian (chicken) species.Tissue-specific differences in the distribution of the lysine-rich histones were studied in liver, kidney, spleen, and thymus tissues of the rat; liver, spleen, and thymus of the calf; and liver, spleen, and erythrocytes of the chicken.The lysine-rich histone fractions were extracted with aqueous trichloracetic acid from 0.14 M NaCl-washed tissue homogenates and isolated nuclei.The extracts were fractionated by gradient elution chromatography on Amberlite IRC-50 with a linear gradient of guanidmium chloride.Species-specific lysine-rich histone components were observed in the elution profdes for the spleen of calf, rat, cat, and chicken which showed three, five, four, and five distinct components, respectively.Studies on the electrophoretic mobility of the whole lyslne-rich histone fractions in polyacrylamide gels showed that the rat spleen fraction contained a component not found in either calf spleen or chicken spleen.In addition, the chicken spleen fraction contained a component not found in the calf spleen fraction.Amino acid analysis of the individual chromatographic components of four different species showed that the over-all compositions were remarkably similar except for a single component found in four tissues of the rat.Treatment of this component with cyanogen bromide indicated that methionine was an integral part of the primary structure.This is the first report of the presence of methionine in a purified lysine-rich histone from any source.Quantitative differences were found between a number of corresponding lysine-rich histones of diEerent tissues of the same species, both mammalian and avian, but the complement of histones for a given species was identical in all tissues studied.Planlmetric analysis of duplicate chromatographic profles of three separate preparations of the rat thymus, spleen, liver, and kidney fractions showed that the thymus fraction contained a 4-to 7-fold greater amount of Compo-