Na+-NQR / Na+ transporter / inhibitor / oxidoreductase / drug resistant / MEMBRANE PROTEIN
Function / homology
Function and homology information
riboflavin binding / NADH:ubiquinone reductase (Na+-transporting) / Gram-negative-bacterium-type cell wall / oxidoreductase activity, acting on NAD(P)H, quinone or similar compound as acceptor / sodium ion transport / FAD binding / respiratory electron transport chain / transmembrane transport / 2 iron, 2 sulfur cluster binding / FMN binding ...riboflavin binding / NADH:ubiquinone reductase (Na+-transporting) / Gram-negative-bacterium-type cell wall / oxidoreductase activity, acting on NAD(P)H, quinone or similar compound as acceptor / sodium ion transport / FAD binding / respiratory electron transport chain / transmembrane transport / 2 iron, 2 sulfur cluster binding / FMN binding / electron transfer activity / metal ion binding / plasma membrane Similarity search - Function
Japan Agency for Medical Research and Development (AMED)
JP23ama121001
Japan
Citation
Journal: Biochemistry / Year: 2025 Title: Structural Elucidation of the Mechanism for Inhibitor Resistance in the Na-Translocating NADH-Ubiquinone Oxidoreductase from . Authors: Moe Ishikawa-Fukuda / Jun-Ichi Kishikawa / Takahiro Masuya / Takeshi Ito / Nicole L Butler / Danielle McFee / Takayuki Kato / Blanca Barquera / Hideto Miyoshi / Masatoshi Murai / Abstract: Na-translocating NADH-ubiquinone oxidoreductase (Na-NQR) is a unique redox-driven Na-pump. Since this enzyme is exclusively found in prokaryotes, including the human pathogens and , it is a ...Na-translocating NADH-ubiquinone oxidoreductase (Na-NQR) is a unique redox-driven Na-pump. Since this enzyme is exclusively found in prokaryotes, including the human pathogens and , it is a promising target for highly selective antibiotics. Korormicin A, a natural product, and a specific and potent inhibitor of Na-NQR, may become a lead compound for the relevant drug design. We previously showed that the G141A mutation in the NqrB subunit (NqrB-G141A) confers moderate resistance to korormicin A (about 100-fold). However, the efficiency of photoaffinity labeling of the mutant enzyme by a photoreactive korormicin derivative was the same as in the wild-type enzyme. Because of these apparently conflicting results, the molecular mechanism underlying the korormicin A-resistance remains elusive. In the present study, we determined the cryo-EM structure of the NqrB-G141A mutant in the presence of bound korormicin A, and compared it to the corresponding structure from the wild-type enzyme. The toxophoric moiety of korormicin A binds to the mutant enzyme similarly to how it binds to the wild type. However, the added bulk of the alanine-141 excludes the alkyl side chain from the binding cavity, resulting in a decrease in the binding affinity. In fact, isothermal titration calorimetry revealed that the binding affinity of korormicin to the NqrB-G141A mutant is significantly weaker compared to the wild-type. Altogether, we conclude that the inhibitory potency of korormicin A is weaker in the NqrB-G141A mutant due to the decrease in its binding affinity to the altered binding cavity.
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