Mg2+-, Ca2+-dependent unwinding of DNA by poly-L-glutamic acid

Abstract In order to examine a possibility that the high acidic amino acid region in the nonhistone protein HMG(1+2) is concerned with the Mg 2+ -, or Ca 2+ -dependent unwinding of DNA by the HMG(1+2) (1,2), poly-L-glutamic acid was employed as an acidic model peptide for thermal melting temperature analysis. The poly-L-glutamic acid bound to DNA either in the presence or absence of Mg 2+ . The poly-L-glutamic acid unwound DNA double-helix to a similar extent to HMG(1+2) in the presence of Mg 2+ or Ca 2+ , but not in the absence of them. These results may suggest that the high acidic amino acid region in HMG(1+2) participates in Mg 2+ -, Ca 2+ -dependent unwinding of DNA double-helix.