Division of Allergy and Infectious Diseases, Center for Emerging and Re-emerging Infectious Diseases, Department of Medicine, University of Washington, Seattle, WA 98109, USA.
Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.
Acta Crystallogr F Struct Biol Commun. 2024 Aug 1;80(Pt 8):173-182. doi: 10.1107/S2053230X24006472. Epub 2024 Jul 11.
Klebsiella pneumoniae (Kp) is an infectious disease pathogen that poses a significant global health threat due to its potential to cause severe infections and its tendency to exhibit multidrug resistance. Understanding the enzymatic mechanisms of the oxygen-insensitive nitroreductases (Kp-NRs) from Kp is crucial for the development of effective nitrofuran drugs, such as nitrofurantoin, that can be activated as antibiotics. In this paper, three crystal structures of two Kp-NRs (PDB entries 7tmf/7tmg and 8dor) are presented, and an analysis of their crystal structures and their flavin mononucleotide (FMN)-binding mode is provided. The structures with PDB codes 7tmf (Kp-NR1a), 7tmg (Kp-NR1b) and 8dor (Kp-NR2) were determined at resolutions of 1.97, 1.90 and 1.35 Å, respectively. The Kp-NR1a and Kp-NR1b structures adopt an αβ fold, in which four-stranded antiparallel β-sheets are surrounded by five helices. With domain swapping, the β-sheet was expanded with a β-strand from the other molecule of the dimer. The difference between the structures lies in the loop spanning Leu173-Ala185: in Kp-NR1a the loop is disordered, whereas the loop adopts multiple conformations in Kp-NR1b. The FMN interactions within Kp-NR1/NR2 involve hydrogen-bond and π-stacking interactions. Kp-NR2 contains four-stranded antiparallel β-sheets surrounded by eight helices with two short helices and one β-sheet. Structural and sequence alignments show that Kp-NR1a/b and Kp-NR2 are homologs of the Escherichia coli oxygen-insensitive NRs YdjA and NfnB and of Enterobacter cloacae NR, respectively. By homology inference from E. coli, Kp-NR1a/b and Kp-NR2 may detoxify polynitroaromatic compounds and Kp-NR2 may activate nitrofuran drugs to cause bactericidal activity through a ping-pong bi-bi mechanism, respectively.
肺炎克雷伯菌（Kp）是一种传染性疾病病原体，由于其导致严重感染的潜力及其表现出的多药耐药性，对全球健康构成重大威胁。了解肺炎克雷伯菌中氧不敏感硝基还原酶（Kp-NRs）的酶促机制对于开发有效的硝基呋喃类药物（如呋喃妥因）至关重要，这些药物可以作为抗生素被激活。本文介绍了两种肺炎克雷伯菌的硝基还原酶（Kp-NRs）的三个晶体结构（PDB 条目 7tmf/7tmg 和 8dor），并对其晶体结构及其黄素单核苷酸（FMN）结合模式进行了分析。带有 PDB 代码 7tmf（Kp-NR1a）、7tmg（Kp-NR1b）和 8dor（Kp-NR2）的结构分别在 1.97、1.90 和 1.35Å 的分辨率下确定。Kp-NR1a 和 Kp-NR1b 结构采用 αβ 折叠，其中四链反平行 β-折叠由五个螺旋包围。通过结构域交换，β-折叠由二聚体中另一个分子的β-链扩展。结构之间的差异在于跨越 Leu173-Ala185 的环：在 Kp-NR1a 中，该环无序，而在 Kp-NR1b 中，该环采用多种构象。Kp-NR1/NR2 中的 FMN 相互作用涉及氢键和 π-堆积相互作用。Kp-NR2 包含四链反平行 β-折叠，由八个螺旋包围，其中有两个短螺旋和一个 β-折叠。结构和序列比对表明，Kp-NR1a/b 和 Kp-NR2 分别是大肠杆菌氧不敏感 NRs YdjA 和 NfnB 和阴沟肠杆菌 NR 的同源物。根据大肠杆菌的同源推断，Kp-NR1a/b 和 Kp-NR2 可能通过苯并二氮杂卓双加氧酶机制解毒多硝基芳烃化合物，而 Kp-NR2 可能通过乒乓双酶机制激活硝基呋喃类药物以产生杀菌活性。
