Amino-acid Sequence of Slightly Lysine-rich Histone

KNOWLEDGE of the amino-acid sequence of histones is required to understand the molecular mechanisms of their function in the cell nucleus. Only recently, however, has it become possible to separate quantitatively the individual histones and to characterize the homogeneous components1–12. We have developed a new chromatographic method using carboxymethyl-cellulose (CMC) with a linearly decreasing concentration of ethanol in 2.6 M formic acid containing 0.1 M sodium formate as an eluting agent for fractionation and a new polyacrylamide gel electrophoretic system for the characterization of the histone fractions5. We have found that calf-thymus histones comprise five main types which differ in amino acid composition and in electrophoretic mobility: a glycine-rich, arginine-rich histone (also known as f2al or IV); a glutamic-acid-rich, arginine-rich histone (fe or III); a leucine-rich, intermediate type histone (f2a2 or IIb1); a serine-rich, slightly lysine-rich histone (f2b or IIb2); and an alanine-rich, very lysine-rich histone (f1 or I).