Brekasis Dimitris, Paget Mark S B
Department of Biochemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK.
EMBO J. 2003 Sep 15;22(18):4856-65. doi: 10.1093/emboj/cdg453.
We describe the identification of Rex, a novel redox-sensing repressor that appears to be widespread among Gram-positive bacteria. In Streptomyces coelicolor Rex binds to operator (ROP) sites located upstream of several respiratory genes, including the cydABCD and rex-hemACD operons. The DNA-binding activity of Rex appears to be controlled by the redox poise of the NADH/NAD+ pool. Using electromobility shift and surface plasmon resonance assays we show that NADH, but not NAD+, inhibits the DNA-binding activity of Rex. However, NAD+ competes with NADH for Rex binding, allowing Rex to sense redox poise over a range of NAD(H) concentrations. Rex is predicted to include a pyridine nucleotide-binding domain (Rossmann fold), and residues that might play key structural and nucleotide binding roles are highly conserved. In support of this, the central glycine in the signature motif (GlyXGlyXXGly) is shown to be essential for redox sensing. Rex homologues exist in most Gram-positive bacteria, including human pathogens such as Staphylococcus aureus, Listeria monocytogenes and Streptococcus pneumoniae.
我们描述了一种新型氧化还原感应阻遏蛋白Rex的鉴定，它似乎在革兰氏阳性细菌中广泛存在。在天蓝色链霉菌中，Rex与几个呼吸基因上游的操纵子（ROP）位点结合，包括cydABCD和rex-hemACD操纵子。Rex的DNA结合活性似乎受NADH/NAD+池的氧化还原平衡控制。通过电泳迁移率变动分析和表面等离子体共振分析，我们发现NADH而非NAD+会抑制Rex的DNA结合活性。然而，NAD+与NADH竞争Rex的结合，使Rex能够在一系列NAD（H）浓度范围内感知氧化还原平衡。预计Rex包含一个吡啶核苷酸结合结构域（罗斯曼折叠），可能发挥关键结构和核苷酸结合作用的残基高度保守。支持这一点的是，特征基序（GlyXGlyXXGly）中的中心甘氨酸被证明对氧化还原感应至关重要。Rex同源物存在于大多数革兰氏阳性细菌中，包括人类病原体，如金黄色葡萄球菌、单核细胞增生李斯特菌和肺炎链球菌。
