Calorimetric studies of the interactions of linker histone H10 and its carboxyl (H10-C) and globular (H10-G) domains with calf-thymus DNA

Histone H1 is a chromatin protein found in most eukaryotes. ITC and CD have been used to study the binding of H1(0) and its C-terminal, H1(0)-C, and globular, H1(0)-G, domains to a highly polymerized DNA. ITC results indicate that H1(0) and H1(0)-C bind tightly to DNA (K-a approximate to 1 x 10(7)), with an unfavorable Delta H (Delta H approximate to +22 kcal/mol) and a favorable Delta S (-T Delta S approximate to -30 kcal/mol). Binding H1(0)-G to DNA at 25 degrees C is calorimetrically silent. A multiple independent site model fits the ITC data, with the anomaly in the data near saturation attributed to rearrangement of bound H1, maximizing the number of binding sites. CD experiments indicate that H1(0)/DNA and H1(0)-C/DNA complexes form with little change in protein structure but with some DNA restructuring. Salt dependent ITC experiments indicate that the electrostatic contribution to binding H1(0) or H1(0)-C is small ranging from 6% to 17% of the total Delta G. (C) 2013 Elsevier B.V. All rights reserved.