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Methionine sulfoxide reductase B from Corynebacterium diphtheriae catalyzes sulfoxide reduction via an intramolecular disulfide cascade

Tossounian, M-A; Khanh Truong, A-C; Buts, L; Wahni, K; Mourenza, Á; Leermakers, M; Vertommen, D; ... Messens, J; + view all (2020) Methionine sulfoxide reductase B from Corynebacterium diphtheriae catalyzes sulfoxide reduction via an intramolecular disulfide cascade. Journal of Biological Chemistry 10.1074/jbc.RA119.012438. (In press). Green open access

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Abstract

Corynebacterium diphtheriae is a human pathogen that causes diphtheria. In response to immune system–induced oxidative stress, C. diphtheriae expresses antioxidant enzymes, among which are methionine sulfoxide reductase (Msr) enzymes, which are critical for bacterial survival in the face of oxidative stress. Although some aspects of the catalytic mechanism of the Msr enzymes have been reported, several details still await full elucidation. Here, we solved the solution structure of C. diphtheriae MsrB (Cd-MsrB) and unraveled its catalytic and oxidation-protection mechanisms. Cd-MsrB catalyzes methionine sulfoxide reduction involving three redox-active cysteines. Using NMR heteronuclear single-quantum coherence (HSQC) spectra, kinetics, biochemical assays, and MS analyses, we show that the conserved nucleophilic residue Cys122 is S-sulfenylated after substrate reduction, which is then resolved by a conserved cysteine, Cys66, or by the non-conserved residue Cys127. We noted that the overall structural changes during the disulfide cascade expose the Cys122–Cys66 disulfide to recycling through thioredoxin (Trx). In the presence of hydrogen peroxide, Cd-MsrB formed reversible intra- and intermolecular disulfides without losing its Cys-coordinated Zn2+, and only the non-conserved Cys127 reacted with the low-molecular-weight (LMW) thiol mycothiol, protecting it from overoxidation. In summary, our structure–function analyses reveal critical details of the Cd-MsrB catalytic mechanism, including a major structural rearrangement that primes the Cys122–Cys66 disulfide for Trx reduction and a reversible protection against excessive oxidation of the catalytic cysteines in Cd-MsrB through intra- and intermolecular disulfide formation and S-mycothiolation.

Type: Article
Title: Methionine sulfoxide reductase B from Corynebacterium diphtheriae catalyzes sulfoxide reduction via an intramolecular disulfide cascade
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1074/jbc.RA119.012438
Publisher version: https://doi.org/10.1074/jbc.RA119.012438
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: redox mechanism, biochemistry, methionine sulfoxide, enzyme mechanism, NMR solution structure, hydrogen peroxide, Corynebacterium diphtheriae, S-mycothiolation, antioxidant system, oxidative stress
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Structural and Molecular Biology
URI: https://discovery.ucl.ac.uk/id/eprint/10090971
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