Cui Qiu, Tong Yufeng, Xue Hong, Huang Li, Feng Yingang, Wang Jinfeng
National Laboratory of Biomacromolecules, Center for Molecular Biology, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, 100101 Beijing, China.
J Biol Chem. 2003 Dec 19;278(51):51015-22. doi: 10.1074/jbc.M308510200. Epub 2003 Sep 30.
The DNA-binding protein Ssh10b from the hyperthermophilic archaeon Sulfolobus shibatae is a member of the Sac10b family, which has been speculated to be involved in the organization of the chromosomal DNA in Archaea. Ssh10b affects the DNA topology in a temperature dependent fashion that has not been reported for any other DNA-binding proteins. Heteronuclear NMR and site-directed mutagenesis were used to analyze the structural basis of the temperature-dependent Ssh10b-DNA interaction. The data analysis indicates that two forms of Ssh10b homodimers co-exist in solution, and the slow cis-trans isomerization of the Leu61-Pro62 peptide bond is the key factor responsible for the conformational heterogeneity of the Ssh10b homodimer. The T-form dimer, with the Leu61-Pro62 bond in the trans conformation, dominates at higher temperature, whereas population of the C-form dimer, with the bond in the cis conformation, increases on decreasing the temperature. The two forms of the Ssh10b dimer show the same DNA binding site but have different conformational features that are responsible for the temperature-dependent nature of the Ssh10b-DNA interaction.
来自嗜热古菌柴田硫化叶菌的DNA结合蛋白Ssh10b是Sac10b家族的成员，据推测该家族参与古菌染色体DNA的组织。Ssh10b以温度依赖的方式影响DNA拓扑结构，这在其他任何DNA结合蛋白中都未被报道过。利用异核核磁共振和定点诱变分析了Ssh10b与DNA相互作用的温度依赖性的结构基础。数据分析表明，两种形式的Ssh10b同型二聚体在溶液中共存，Leu61-Pro62肽键的缓慢顺反异构化是导致Ssh10b同型二聚体构象异质性的关键因素。T型二聚体中Leu61-Pro62键处于反式构象，在较高温度下占主导地位，而C型二聚体中该键处于顺式构象，其数量随温度降低而增加。Ssh10b二聚体的两种形式具有相同的DNA结合位点，但具有不同的构象特征，这导致了Ssh10b与DNA相互作用的温度依赖性。
