On the possibility that H1 histone interaction with DNA occurs through phosphates connecting lysine and arginine side chain groups.

Gel filtration and velocity of sedimentation analyses on native and on lysine- and arginine-modified forms of the annelid worm Chaetopterus variopedatus sperm H1 histone indicate that anion-mediated lysine-arginine interactions play a relevant role in the stabilization of the oligomeric states of the molecule. CD spectroscopy shows that phosphate anions are at least an order of magnitude more efficient than chloride as negatively charged groups connecting H1 lysines and arginines. Acetylation of lysines, although not altering grossly the H1 properties, causes a tenfold decrease of the structuring efficiency of phosphates. This suggests that DNA phosphates may be sandwiched between lysine and arginine groups of H1 histone when this molecule binds to chromatin, constituting a relevant parameter for the reciprocal stabilization of the protein and of the chromatin higher order structures.