Chivers Peter T, Sauer Robert T
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Chem Biol. 2002 Oct;9(10):1141-8. doi: 10.1016/s1074-5521(02)00241-7.
E. coli NikR repressor binds operator DNA in a nickel-dependent fashion. The pM affinity of NikR for nickel is mediated by its C-terminal 86 residues. Nickel binding induced additional secondary structure, decreased the compactness, and increased the stability of NikR. Tetramer formation by the C-terminal domain and intact NikR did not require nickel. High-affinity nickel binding decreased the NikR concentration needed to half maximally protect operator DNA from undetectable levels to 30 nM. The intracellular concentration of NikR in E. coli is high enough that saturation of the high-affinity nickel sites should lead to substantial occupancy of the nik operator. Nickel binding to a set of low-affinity NikR sites resulted in an additional large increase in operator affinity and substantially increased the size of the NikR footprint on the operator.
大肠杆菌NikR阻遏蛋白以镍依赖的方式结合操纵子DNA。NikR对镍的pM亲和力由其C末端的86个残基介导。镍结合诱导了额外的二级结构，降低了紧密性，并增加了NikR的稳定性。C末端结构域和完整的NikR形成四聚体不需要镍。高亲和力的镍结合将使操纵子DNA受到半最大保护所需的NikR浓度从不可检测水平降低到30 nM。大肠杆菌中NikR的细胞内浓度足够高，以至于高亲和力镍位点的饱和应导致nik操纵子的大量占据。镍与一组低亲和力的NikR位点结合导致操纵子亲和力进一步大幅增加，并显著增加了NikR在操纵子上的足迹大小。
