van der Velden Tijn T, Kayastha Kanwal, Waterham Caspar Y J, Brünle Steffen, Jeuken Lars J C
Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands.
Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands.
J Biol Chem. 2025 Feb;301(2):108094. doi: 10.1016/j.jbc.2024.108094. Epub 2024 Dec 18.
Cytochrome bd from Mycobacterium tuberculosis (Mtbd) is a menaquinol oxidase that has gained interest as an antibiotic target because of its importance in survival under infectious conditions. Mtbd contains a characteristic disulfide bond that has been hypothesized to allow for Mtbd activity regulation at the enzymatic level, possibly helping M. tuberculosis to rapidly adapt to the hostile environment of the phagosome. Here, the role of the disulfide bond and quinone specificity have been determined by reconstitution of a minimal respiratory chain and the single-particle cryo-EM structure in the disulfide-reduced form. Mtbd was shown to be specific for menaquinone, while regulation by reduction of the Q-loop disulfide bond decreased oxidase activity up to 90%. Structural analysis shows that a salt bridge unique to Mtbd keeps the Q-loop partially structured in its disulfide-reduced form, which could facilitate the rapid activation of Mtbd upon exposure to reactive oxygen species. We signify Mtbd as the first redox sensory terminal oxidase and propose that this helps M. tuberculosis in the defense against reactive oxygen species encountered during infection.
结核分枝杆菌（Mtbd）的细胞色素bd是一种甲萘醌氧化酶，因其在感染条件下对生存的重要性而成为备受关注的抗生素靶点。Mtbd含有一个特征性二硫键，据推测该二硫键可在酶水平上调节Mtbd的活性，可能有助于结核分枝杆菌快速适应吞噬体的恶劣环境。在此，通过重建最小呼吸链和二硫键还原形式的单颗粒冷冻电镜结构，确定了二硫键的作用和醌特异性。结果表明，Mtbd对甲萘醌具有特异性，而通过还原Q环二硫键进行的调节可使氧化酶活性降低达90%。结构分析表明，Mtbd特有的盐桥使Q环在其二硫键还原形式下保持部分结构，这可能有助于Mtbd在暴露于活性氧时快速激活。我们将Mtbd视为首个氧化还原感应末端氧化酶，并提出这有助于结核分枝杆菌抵御感染期间遇到的活性氧。
