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1. The glycine-rich, arginine-rich histone from calf thymus was hydrolyzed with chymotrypsin; the peptides produced were fractionated on Sephadex G-25. The peptides containing the aromatic amino acids were purified by rechromatography on Sephadex G-25 and Aminex A-4 columns and by peptide mapping. 2. The six aromatic amino acids of the glycine-rich, arginine-rich histone were accounted for in eight peptides, including those found in the preceding study (Sautiere et al., J. Biol. Chem., 243, 5899 (1968)). The sequence and order of these peptides were determined by analysis of the overlapping tryptic peptides. 3. All the aromatic amino acids were found to be in the carboxyl half of the glycine-rich, arginine-rich histone. The sequence of this portion, which includes 53 amino acids, is Ile-Tyr-Glu-Glu-Thr-Arg-Gly-Val-Leu-Lys-Val-Phe-Leu-Glu-Asx-Val-Ile-Arg-Asp-Ala-Val-Thr-Tyr-Thr-Glu-His-Ala-Lys-Arg-Lys-Thr-Val-Thr-Ala-Met-Asp-Val-Val-Tyr-Ala-Leu-Lys-Arg-Gln-Gly-Arg-Thr-Leu-Tyr-Gly-Phe-Gly-Gly-COOH.

1. The amino acid sequence of the amino-terminal portion of the glycine-rich, arginine-rich histone (Residues 1 to 49) has been determined from studies on the tryptic, chymotryptic, and thermolysin peptides. This sequence overlaps with that of the carboxylterminal portion (Residues 50 to 102) defined previously to give the following sequence: acetylSer-Gly-Arg-Gly-Lys-Gly-Gly-Lys-Gly-Leu-Gly-Lys-Gly-Gly-Ala-Lys(Ac)-Arg-His-Arg-Lys(Me)-Val-Leu-ArgAsp-Asn-Ile-Gln-Gly-Ile-Thr-Lys-Pro-Ala-Ile-Arg-Arg-Leu-Ala-Arg-Arg-Gly-Gly-Val-Lys-Arg-Ile-Ser-Gly-Leu-Ile-Tyr-Glu-Glu-Thr-Arg-Gly-Val-Leu-Lys-Val-Phe-Leu-Glu-Asn-Val-Ile-Arg-Asp-Ala-Val-Thr-Tyr-Thr-Glu-His-Ala-Lys-Arg-Lys-Thr-Val-Thr-Ala-Met-Asp-Val-Val-Tyr-Ala-Leu-Lys-Arg-Gln-Gly-Arg-Thr-Leu-Tyr-Gly-Phe-Gly-Gly-COOH. 2. This sequence agrees with that reported recently by DeLange, Fambrough, Smith, and Bonner (J. Biol. Chem., 244, 319 (1969)) except that the arginine residue they placed at position 44 is found in position 40 (and is italicized) in the above sequence. 3. Four clusters of basic residues (underlined) were present in this sequence. The cluster in the amino-terminal portion contained both the modified amino acids e-Nacetyllysine and e-N-methyllysine at positions 16 and 20. The acetyllysine was present in approximately half of the glycine-rich, arginine-rich histone molecules; the methylated lysine position contained mono and dimethyl groups in a ratio of 1:3. This microheterogeneity makes a total of four possible species of the glycine-rich, arginine-rich histone.

Although the GAR histone itself inhibited the in vitro RNA polymerase system, clusters of basic amino acids isolated from thermolysin digest of calf thymus GAR histone slightly inhibited or stimulated M . leutus and nucleolar RNA polymerase systems. These data indicate that the inhibition of RNA polymerase systems in vitro by the GAR histone is not simply due to a neutralization of the negative charges of the DNA by the positive charges of the histone but may be related to precipitation of rigid, hydrophobic DNA-histone complexes from solution.

1. 1. The glycine-arginine-rich histones isolated from bovine lymphosarcoma and Novikoff hepatoma have been found to have virtually the same amino acid compositions as that of fetal cal thymus and calf thymus published previously 8,9 . 2. 2. The glycine-arginine-rich histones isolated from fetal calf thymus, bovine lymphosarcoma and Novikoff hepatoma were cleaved with cyanogen bromide to yield two peptides. The C-terminal CN-2 peptide for each histone was isolated by the use of Sephadex G-100. The C-terminal CN-2 peptide for each of these three tissues was found to have the same amino acid composition as that from calf thymus 12 . 3. 3. The C-terminal peptides, CN-2, of bovine lymphosarcoma, fetal calf thymus and Novikoff hepatoma were hydrolyzed with trypsin. In each case five peptides were obtained by peptide mapping and ion-exchange chromatography. The amino acid compositions of these peptides were identical for each of the tissues and to that found for calf thymus previously. 4. 4. It was concluded that the C-terminal portion of the glycine-arginine-rich histones isolaetd from these four tissues are identical with each other and with that of pea seedling 11 .