A single amino acid residue controls ROS production in the respiratory Complex I from Escherichia coli. Issue 6 (29th October 2013)

• Record Type: Journal Article
• Authors: Knuuti, Juho; Belevich, Galina; Sharma, Vivek; Bloch, Dmitry A.; Verkhovskaya, Marina
• Is Part Of: Molecular microbiology. Volume 90:Issue 6(2013)
• Page Start: 1190
• Page End: 1200
• Publication Date: 2013-10-29
• Subjects: Molecular microbiology -- Periodicals; 572.829
• DOI: 10.1111/mmi.12424
• Languages: English
• ISSNs: 0950-382X

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p>Reactive oxygen species (ROS) production by respiratory Complex I from <italic>Escherichia coli</italic> was studied in bacterial membrane fragments and in the isolated and purified enzyme, either solubilized or incorporated in proteoliposomes. We found that the replacement of a single amino acid residue in close proximity to the nicotinamide adenine dinucleotide (NADH)‐binding catalytic site (E95 in the NuoF subunit) dramatically increases the reactivity of Complex I towards dioxygen (O₂). In the E95Q variant short‐chain ubiquinones exhibit strong artificial one‐electron reduction at the catalytic site, also leading to a stronger increase in ROS production. Two mechanisms can contribute to the observed kinetic effects: (a) a change in the reactivity of flavin mononucleotide (FMN) towards dioxygen at the catalytic site, and (b) a change in the population of the ROS‐generating state. We propose the existence of two (<italic>closed</italic> and <italic>open</italic>) states of the NAD⁺‐bound enzyme as one feature of the substrate‐binding site of Complex I. The analysis of the kinetic model of ROS production allowed us to propose that the population of Complex I with reduced FMN is always low in the wild‐type enzyme even at low ambient redox potentials, minimizing the rate of reaction with O₂ in contrast to E95Q variant.</p> </abstract>