Histone F2b Research Articles

Effect of Anionic Detergents on the Optical Rotatory Dispersion of Proteins

The ultraviolet Cotton effects of a group of proteins were investigated. Conformational transitions were effected by treating the proteins with decyl and dodecyl sodium sulfates and acid. Whereas the Cotton effects of aldolase, growth hormone, and myoglobin were not significantly altered by the treatment with detergent, considerable changes were observed in the rotatory dispersion curves of alcohol dehydrogenase, deoxyribonuclease, β-lactoglobulin, acid solutions of ovalbumin, histone Fractions F1 and F2b, and soybean trypsin inhibitor. The curves of native alcohol dehydrogenase, deoxyribonuclease, and β-lactoglobulin had negative minima at 228 to 230 mµ and positive maxima at 202 to 205 mµ, indicating the presence of the β conformation. Upon treatment with detergents, the positive maxima were shifted to 198 to 200 mµ, and the amplitudes of both the positive and negative Cotton effects were increased. Changes of a somewhat similar nature were observed upon treating acid solutions of lysozyme and ovalbumin with detergents. In the instance of glutamic dehydrogenase, the changes were complex. The histones and soybean trypsin inhibitor, when in the native state, displayed curves indicating primarily disorganized polypeptide chains; these were converted by the detergents into partial α-helical conformation, as judged from the rotatory dispersion curves.

Studies on nuclear proteins II. Quantitative distribution of histone fractions in various tissues

1. 1. A method for quantitative evaluation of starch-gel electrophoretograms of histones from various tissues was elaborated. Small amounts of AlCl 3 (0.2–0.6 mM) were found to improve the electrophoretic separation of histone fractions and substantially decrease the trailing of the fractions. 2. 2. The contents of the five main electrophoretic bands were determined for calf thymus, rat spleen, rat liver, regenerating rat liver and for Novikoff hepatoma histones. Isolated calf-thymus histone fractions (F1, F2a, F2b, and F3) were used for standard determinations. 3. 3. Various tissues were found to contain different amounts of the five main histone fractions as resolved by teh starch-gel electrophoresis. The very lysine-rich Fraction F1 and the moderately lysine-rich Fraction 2a 11 varied very little in the analyzed tissues. The amount of electrophoretically fast FRaction 2a 1 decreased with the increasing rate of cell division, e.g. in regenerating rat liver or Novikoff hepatoma. The moderately lysine-rich histones F2b showed the greatest variability in the F2 group. Whereas in calf thymus and in rat liver the contents of this fraction were approximately equal, regeneration increased and neoplasia decreased the amount of this histone. The arginine-rich Fraction 3 was found to be substantially increased in the Novikoff hepatoma. It was proposed that if histones function as genetic suppressors, the mechanism regulating histone biosynthesis could serve to control the cellular differentiation.

Studies on nuclear proteins. I. Observations on the tissue and species specificity of the moderately lysine-rich histone fraction 2b.

Abstract 1. 1. Species and tissue specificity of the moderately lysine-rich histone Fraction 2b (F2b) was studied. This fraction was prepared from calf thymus, rat spleen and thymus, Walker carcinosarcoma 256, and from chicken erythrocytes. The purified F2b histones were analyzed; the NH 2 -terminal amino acid was proline, lthe C-terminal amino acid was lysine. The F2b histones are relatively rich in lysine (14.5–15.5%), alanine (10.3–10.8%), and in serine (9.1–9.5%). A characteristic feature of the F2b histones is the nearly equal content of leucine and isoleucine. Other histone fractions reported in the literature have significantly more leucine than isoleucine. 2. 2. The F2b histones were digested with trypsin and the resulting peptides were resolved by paper chromatography and electrophoresis (fingerprinting). Peptide patterns obtained for various tissues were practically identical. Selected tryptic peptides were isolated and analyzed. Comparison of the amino acid composition of corresponding peptides from calf thymus and Walker carcinosarcoma also failed to reveal any tissues or species specificity of the F2b histones in these two tissues. 3. 3. The kinetics of the amino acid release from the C-terminus of teh F2b histones by carboxypeptidases A and B (EC 3.4.2.1 and EC 3.4.2.2) were remarkably similar for histones from various tissues, indicating no species specificity of the C-terminal sequence of amino acids in this fraction. 4. 4. It was concluded that the differences between the primary structure of F2b histones from different tissues are small or negligible and it was suggested that the genetic information coding for these proteins must be very stable, possibly a part of the primordial genome.

Thiol content of calf thymus histone fractions

1. (1)The thiol content and the elementary sulphur content of calf-thymus histone fractions fr, f2a, f2b and f3 have been investigated. 2. (2)Different methods (amperometric silver titration, interaction with the SH-blocking agents N-ethylmaleimide, iodosobenzoate and cystamine, and ability to bind [ 35S]cystamine as mixed disulphide) were employed to demonstrate the presence of thiol groups on certain histones. 3. (3)Fraction f 3, containing 60 μmoles SH per g of protein, was particularly rich in thiol groups. 40% of these groups formed mixed disulphides with cystamine. The f 3 histones contained 0.48% sulphur. 4. (4) The f2a and f2b histones contained small, but significant amounts of SH, whereas only traces of thiol groups were present in Fraction f1. The sulphur contents of these fractions were 0.26, 0.43 and 0.15%, respectively. 5. (5) The results are discussed in relation to the cysteine content of the histones, and from the point of view of radioprotection.