Studies on the role and mode of operation of the very-lysine-rich histone H1 (F1) in eukaryote chromatin. Histone H1 in chromatin and in H1 - DNA complexes.

The nuclear magnetic resonance (NMR) spectrum of chromatin at ionic strengths below about 0.5 M may be attributed solely to its histone H1 component. The effect of various ions and urea on the complex has been investigated using NMR and confirm that the contraction of the complex on increase of ionic strength is largely due to electrostatic interactions. A detailed study of the H1 - DNA complex has also been undertaken. The behaviour of H1 in the two cases is virtually identical, implying that in chromatin the H1 is complexed with the DNA rather than with the other histones. Microcalorimetric measurements reveal that the binding of H1 to DNA is athermic or involves a heat of reaction which is very small indeed.