AN ARCHAEAL DNA-BINDING PROTEIN FROM THERMOPHILIC SULFOLOBUS-ACIDOCALDARIUS FORMS DIFFERENT TYPES OF COMPLEXES WITH DNA

We have characterized a DNA binding protein (DBNP-B) from the thermoac idophilic archaeon Sulfolobus acidocaldarius with respect to its inter action with single and double stranded DNA. The protein in solution ex ists predominantly as dimer as indicated by cross linking studies. Bin ding of DBNP-B to etheno DNA and poly (dA) resulted in fluorescence en hancement and hyperchromicity respectively. Ethidium bromide intercala ted into DNA was completely displaced by DBNP-B. DNase I digestion of dsDNA was increased at subsaturating concentration of the protein and was inhibited at higher concentrations. These results and electron mic roscopy indicate that the protein forms different types of novel compl exes with DNA at different protein to DNA ratios.