Abstact

BACKGROUND Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most serious diseases of rice, and there is a lack of bactericides for controlling this disease. We previously found parthenolide (PTL) is a potential lead for developing bactericides against Xoo, and subunit F of respiratory chain complex I (NuoF) is an important target protein of PTL. However, the binding modes of PTL with NuoF need further elucidation. RESULTS In this study, we obtained the crystal structure of Xoo NuoEF (complex of subunit E and F of respiratory chain complex I) with a resolution of 2.36 Å, which is the first report on the protein structure of NuoEF in plant-pathogenic bacteria. The possible binding sites of PTL with NuoF (Cys105 and Cys187) were predicted with molecular docking and mutated into alanine using a base mismatch method. The mutated proteins were expressed in Escherichia coli and purified with affinity chromatography. The binding abilities of PTL with mutated proteins were investigated via pull-down assay and BIAcore analysis, which revealed that double mutation of Cys105 and Cys187 in NuoF severely affected the binding ability of PTL with NuoF. In addition, the binding modes were further simulated with combined quantum mechanical/molecular mechanical calculations, and the results indicated that PTL may have a stronger binding with Cys105 than Cys187. CONCLUSION NuoEF protein structure of Xoo was resolved, and Cys105 and Cys187 in NuoF are important binding sites of PTL. This study further clarified the action mechanism of PTL against Xoo, and will promote the innovation of bactericides targeting Xoo complex I. © 2024 Society of Chemical Industry.