Effect of DNA binding protein Sshl2 from hyperthermophilic archaeon Sulfolobus shibatae on DNA supercoiling

An 11.5-ku DNA binding protein, designated as Ssh12, was purified from the hyperthermophilic archaeonSulfolobus shibatae by column chromatography in SP Sepharose, DNA cellulose and phosphocellulose. Ssh12 accounts for about 4 % of the total cellular protein. The protein is capable of binding to both negatively supercoiled and relaxed DNAs. Nick closure analysis revealed that Ssh12 constrains negative supercoils upon binding to DNA. While the ability of the protein to constrain supercoils is weak at 22°C, it is enhanced substantially at temperatures higher than 37°C. Both the cellular content and supercoil-constraining ability of Ssh12 suggest that the protein may play an important role in the organization and stabilization of the chromosome ofS. shibatae. Project supported by the National Natural Science Foundation of China (Grant No. 39770006), the Irvine Foundation and the Director’s fund in the Institute of Microbiology, the Chinese Academy of Sciences, and a Grant-in-Aid for Scientists Returning from Abroad from the Chinese Academy of Sciences.