[Interaction of H1 lysine-rich histone fragments with DNA]

The interaction of H1 histone octapeptide 15--22 amino acid sequence fragment and shorter peptides with DNA has been investigated in water low ionic strength solutions (0.01 M NaCl) by means of UV-spectroscopy, circular dichroism (CD), equilibrium dialysis and thermal denaturation. Decreasing of the DNA absorbtion band intensity (260 nm) in complexes with peptides, appearance of the apparent optical density (lambda greater than 320 nm) and presence of the intense positive band at approximately 270 nm in CD-spectra allowed to draw a conclusion that under the action of peptides, the compactization of DNA occurs with the formation of psi + type condensate. The data on equilibrium dialysis and thermal denaturation of the complexes evidence that the compactization decreases the binding degree of DNA and H1 histone fragments and lowers the influence of the latter on DNA helix stabilization.