The N-terminal groups of calf-thymus histones

Abstract

The chief N-terminal groups of the histones extracted from calf-thymus glands are proline and alanine, with smaller amounts of lysine and serine, and still less of 6 other amino acids. The proportions of the serine and lysine end groups have declined markedly in later preparations of the histones. The quantities of the end groups gave an average weight of about 25000/gram molecule of end groups. In a fractionation of the histones, those precipitated by NaCl-NH3 (the arginine-rich histones) mostly have alanine N-terminal groups, whereas those remaining in solution in NaCl-NHg (the lysine-rich histones) mostly have proline end groups.