Studies on the role and mode of operation of the very-lysine-rich histones in eukaryote chromatin. Effect of A and B site phosphorylation on the conformation and interaction of histone H1.

270-MHz proton magnetic resonance has been used to study the effect of phosphorylation of histone H1 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, was found to reduce 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 of serine-37 and serine-105 was found to reduce the strength of binding of the histone to DNA considerably at some ionic strengths.