期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2018
卷号：115
期号：50
页码：E11623-E11632
DOI：10.1073/pnas.1807954115
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Hydrogen peroxide (H2O2) is a strong oxidant capable of oxidizing cysteinyl thiolates, yet only a few cysteine-containing proteins have exceptional reactivity toward H2O2. One such example is the prokaryotic transcription factor OxyR, which controls the antioxidant response in bacteria, and which specifically and rapidly reduces H2O2. In this study, we present crystallographic evidence for the H2O2-sensing mechanism and H2O2-dependent structural transition of Corynebacterium glutamicum OxyR by capturing the reduced and H2O2-bound structures of a serine mutant of the peroxidatic cysteine, and the full-length crystal structure of disulfide-bonded oxidized OxyR. In the H2O2-bound structure, we pinpoint the key residues for the peroxidatic reduction of H2O2, and relate this to mutational assays showing that the conserved active-site residues T107 and R278 are critical for effective H2O2 reduction. Furthermore, we propose an allosteric mode of structural change, whereby a localized conformational change arising from H2O2-induced intramolecular disulfide formation drives a structural shift at the dimerization interface of OxyR, leading to overall changes in quaternary structure and an altered DNA-binding topology and affinity at the catalase promoter region. This study provides molecular insights into the overall OxyR transcription mechanism regulated by H2O2.
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