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linker histone 1 and histone 5 domains; the basic subunit of chromatin is the nucleosome, consisting of an octamer of core histones, two full turns of DNA, a linker histone (H1 or H5) and a variable length of linker DNA; H1/H5 are chromatin-associated proteins that bind to the exterior of nucleosomes and dramatically stabilize the highly condensed states of chromatin fibers; stabilization of higher order folding occurs through electrostatic neutralization of the linker DNA segments, through a highly positively charged carboxy- terminal domain known as the AKP helix (Ala, Lys, Pro); thought to be involved in specific protein-protein and protein-DNA interactions and play a role in suppressing core histone tail domain acetylation in the chromatin fiber
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