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

Abstract
270 MHz PMR was used to study the effect of phosphorylation of histone H1 [calf thymus] in vitro on the structure of isolated H1 molecules and on the interaction of H1 with DNA. Phosphorylation at serine-105, which is located in the globular region of H1, reduced the enthalpy of structure formation from 24 .+-. 2 kcal mol-1 (100 .+-. 8 kJ mol-1) to 13 .+-. 2 kcal mol-1 (55 .+-. 8 kJ mol-1). Phosphorylation at either or both serine-37 and serine-105 reduced the binding strength of the histone to DNA considerably at some ionic strengths.