[Conformational peculiarities of nuclear protein HMGB1 and specificity of its interaction with DNA]. 
Changes in the secondary structure of DNA and non-histone chromosomal protein HMGB1 were studied by circular dichroism and UV spectroscopy.  We have demonstrated that the HMGBI protein is able to change its secondary structure upon binding to DNA.  We estimated the proportion of bound protein on the assumption that there were two spectrally distinguishable forms of the HMGB1 in solution.  The bound protein fraction decreases with increasing protein to DNA ratios (r) from 0.48 at r = 0.13 to 0.06 at r = 2.43.  It has been shown that HMGB1 is able to induce considerable changes in DNA structure even when the amount of the protein directly associated with DNA is low.