PMID: 7016876Jul 10, 1981Paper

Differences among subfractions of H1 histone in their interactions with linear and superhelical DNA. Circular dichroism.

The Journal of Biological Chemistry
L W Liao, R D Cole

Abstract

Interactions between subfractions of ox thymus H1 histone and either linear T7 DNA or superhelical PM2 DNA were studied by measuring the circular dichroism of H1:DNA complexes. H1 subfractions differed from one to the next in their effectiveness at distorting the circular dichroic spectrum of DNA by as much as 3- to 4-fold for both forms of DNA. The order of effectiveness of the subfractions was the same at all ionic strengths between 0.05 M and 0.25 M, but the degree of spectral distortion caused by any of the subfractions was sensitive to the salt concentration. At 0 M NaCl and above 3 M NaCl, there was little or no distortion of the spectrum of DNA by any subfraction; the maximum effectiveness for all of the subfractions was at 0.15 M to 0.2 M NaCl whether the DNA was linear or superhelical. Between 0 M and 0.15 M NaCl, the H1 subfractions in free solution underwent a conformational change from a substantially unfolded state to one that is presumably the native state. This was revealed by circular dichroism. In part, this folding of the protein molecules must account for the effect of salt on the ability of H1 to distort the circular dichroism of DNA when the two macromolecules are brought together in complex formation. The ...Continue Reading

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