X-ray structure of a Rex-family repressor/NADH complex insights into the mechanism of redox sensing
X-ray structure of a Rex-family repressor/NADH complex insights into the mechanism of redox sensing
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DOI：
10.1016/j.str.2004.10.012
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发表时间：
2005-01-01
期刊：
影响因子：
5.7
通讯作者：
Kielkopf, CL
中科院分区：
文献类型：
--
作者：
Sickmier, EA;Brekasis, D;Kielkopf, CL
氧化还原敏感阻遏物雷克斯响应细胞内NADH/NAD（+）氧化还原平衡调节呼吸基因的转录。作为阐明NADH/NAD（+）感应的分子机制的一步，已在2.9埃分辨率下测定了与效应物NADH结合的水生栖热菌雷克斯（T-雷克斯）的X射线结构。雷克斯霸王龙的C-末端结构域的折叠是NAD（H）依赖性酶的特征，而N-末端结构域类似于有翼螺旋DNA结合基序。雷克斯霸王龙二聚化主要由“结构域交换”α螺旋介导。每个NADH分子与二聚体界面附近的C-末端结构域结合。与NAD（OH）依赖性酶相反，烟酰胺深埋在疏水口袋中，似乎阻止底物进入。我们发现T-雷克斯与雷克斯操纵子结合，并且NADH而不是NAD（+）抑制T-雷克斯/DNA结合活性。雷克斯家族成员的氧化还原传感机制与NAD（H）依赖性酶的结构域闭合相似。
The redox-sensing repressor Rex regulates transcription of respiratory genes in response to the intracellular NADH/NAD(+) redox poise. As a step toward elucidating the molecular mechanism of NADH/NAD(+) sensing, the X-ray structure of Thermus aquaticus Rex (T-Rex) bound to effector NADH has been determined at 2.9 Angstrom resolution. The fold of the C-terminal domain of T-Rex is characteristic of NAD(H)-dependent enzymes, whereas the N-terminal domain is similar to a winged helix DNA binding motif. T-Rex dimerization is primarily mediated by "domain-swapped" alpha helices. Each NADH molecule binds to the C-terminal domain near the dimer interface. In contrast to NAD(H dependent enzymes, the nicotinamide is deeply buried within a hydrophobic pocket that appears to preclude substrate entry. We show that T-Rex binds to the Rex operator, and NADH but not NAD(+) inhibits T-Rex/DNA binding activity. A mechanism for redox sensing by Rex family members is proposed by analogy with domain closure of NAD(H)-dependent enzymes.