The bacterial strain Pseudomonas sp. MC1 harbors an 81-kb metabolic plasmid, which encodes enzymes involved in the conversion of naphthalene to salicylate. Of these, the enzyme NahB (cis-dihydrodiol naphthalene dehydrogenase), which catalyzes the second reaction of this pathway, binds to various substrates such as cis-1,2-dihydro-1,2-dihydroxy-naphthalene (1,2-DDN), cis-2,3-dihydro-2,3-dihydroxybiphenyl (2,3-DDB), and 3,4-dihydro-3,4-dihydroxy-2,2',5,5'-tetrachlorobiphenyl (3,4-DD-2,2',5-5-TCB). However, the mechanism underlying its broad substrate specificity is unclear owing to the lack of structural information. Here, we determined the first crystal structures of NahB in the absence and presence of NAD+ and 2,3-dihydroxybiphenyl (2,3-DB). Structure analysis suggests that the flexible substrate-binding loop allows NahB to accommodate diverse substrates. Furthermore, we defined the initial steps of substrate recognition and identified the early substrate-binding site in the substrate recognition process through the complex structure with ligands.

中文翻译：

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假单胞菌（Pseudomonas sp。）的顺式-二氢二醇萘脱氢酶（NahB）的晶体结构。MC1：洞悉底物的早期结合过程。

细菌菌株假单胞菌属。MC1带有一个81kb的代谢质粒，该质粒编码与萘转化为水杨酸酯有关的酶。其中，催化该途径第二反应的酶NahB（顺式-二氢二醇萘脱氢酶）与各种底物结合，例如顺式1,2,2-二氢-1,2-二羟基萘（1,2-DDN） ），顺式2,3-二氢-2,3-二羟基联苯（2,3-DDB）和3,4-二氢-3,4-二羟基-2,2'，5,5'-四氯联苯（3， 4-DD-2,2'，5-5-TCB）。然而，由于缺乏结构信息，尚不清楚其广泛的底物特异性的潜在机制。在这里，我们确定了在不存在和存在NAD +和2,3-二羟基联苯（2,3-DB）的情况下NahB的第一个晶体结构。结构分析表明，柔性底物结合环使NahB可以容纳各种底物。此外，我们定义了底物识别的初始步骤，并通过具有配体的复杂结构识别了底物识别过程中的早期底物结合位点。