Studies on the Role and Mode of Operation of the Very‐Lysine‐Rich Histone H1 in Eukaryote Chromatin

Abstract

Limited digestion with trypsin of both calf thymus H1 histone and the fragment 1-120 of the H1 molecule has resulted in the isolation of the fragment 35-120. This fragment assumes a globular structure under physiological conditions of pH and ionic strength. The variable N-terminal portion of the molecule, up to residue 34, is not required for the formation of the H1 globular structure. Proton nuclear magnetic resonance (NMR) and ultracentrifugation studies show that the H1 histone molecule consists of three distinct structural domains under structuring conditions: a random coil ‘nose’ consisting of 35 to 40 residues from the N-terminal end; a globular ‘head’ involving the next approximately 80 residues; and a random-coil ‘tail’ of the remainder of the molecule.