Herbig A F, Helmann J D
Department of Microbiology, Cornell University, Ithaca, NY 14853-8101, USA.
Mol Microbiol. 2001 Aug;41(4):849-59. doi: 10.1046/j.1365-2958.2001.02543.x.
The inducible response to H(2)O(2) stress in Bacillus subtilis is under the control of PerR, one of three Fur homologues in this organism. PerR was purified in both an inactive, metal-dependent form and an active, metal-containing form as determined using DNA-binding assays. Active PerR contains both zinc and iron and is designated PerR:Zn,Fe. Added manganous ion competes for binding to the iron site and can restore DNA-binding activity to the metal-dependent form of PerR, presumably generating PerR:Zn,Mn. The DNA-binding activity of PerR:Zn,Fe is eliminated by exposure to H(2)O(2) whereas PerR:Zn,Mn is comparatively resistant. DNA-binding activity can be restored by a thiol-reducing agent, suggesting that redox-active cysteines are involved in peroxide sensing. Experiments using reporter fusions demonstrate that elevated levels of manganese repress PerR regulon genes and prevent their full induction by H(2)O(2). In contrast, in cells grown with iron supplementation, a PerR-repressed gene is completely derepressed by H(2)O(2). These results are consistent with the idea that the intracellular form of the PerR metalloprotein, and therefore its hydrogen peroxide sensitivity, can be altered by growth conditions.
枯草芽孢杆菌中对H₂O₂胁迫的诱导反应受PerR调控，PerR是该生物体中三种Fur同源物之一。通过DNA结合试验测定，PerR以无活性的、金属依赖性形式和有活性的、含金属形式被纯化出来。活性PerR同时含有锌和铁，被命名为PerR:Zn,Fe。添加的锰离子竞争与铁位点的结合，并能将DNA结合活性恢复到PerR的金属依赖性形式，推测生成PerR:Zn,Mn。PerR:Zn,Fe的DNA结合活性通过暴露于H₂O₂而被消除，而PerR:Zn,Mn则相对具有抗性。DNA结合活性可通过硫醇还原剂恢复，这表明氧化还原活性半胱氨酸参与了过氧化物传感。使用报告基因融合的实验表明，锰水平的升高会抑制PerR调控子基因，并阻止它们被H₂O₂完全诱导。相反，在补充铁的情况下生长的细胞中，一个被PerR抑制的基因会被H₂O₂完全去抑制。这些结果与以下观点一致，即PerR金属蛋白的细胞内形式，以及因此其对过氧化氢的敏感性，可以被生长条件改变。
