期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 114, 期 9, 页码 2355-2360出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1614133114
关键词
sulfide sensor; photosynthesis regulation; reactive sulfur species; purple bacteria; Rhodobacter
资金
- Japan Science Society Sasagawa Fellowship [16K14694, 16H03280]
- NIH [GM040941, GM097225, GM118157]
- Grants-in-Aid for Scientific Research [16K14694, 16H03280] Funding Source: KAKEN
Sulfide was used as an electron donor early in the evolution of photosynthesis, with many extant photosynthetic bacteria still capable of using sulfur compounds such as hydrogen sulfide (H2S) as a photosynthetic electron donor. Although enzymes involved in H2S oxidation have been characterized, mechanisms of regulation of sulfide-dependent photosynthesis have not been elucidated. In this study, we have identified a sulfide-responsive transcriptional repressor, SqrR, that functions as a master regulator of sulfide-dependent gene expression in the purple photosynthetic bacterium Rhodobacter capsulatus. SqrR has three cysteine residues, two of which, C41 and C107, are conserved in SqrR homologs from other bacteria. Analysis with liquid chromatography coupled with an electrospray-interface tandem-mass spectrometer reveals that SqrR forms an intramolecular tetrasulfide bond between C41 and C107 when incubated with the sulfur donor glutathione persulfide. SqrR is oxidized in sulfide-stressed cells, and tetrasulfide-cross-linked SqrR binds more weakly to a target promoter relative to unmodified SqrR. C41S and C107S R. capsulatus SqrRs lack the ability to respond to sulfide, and constitutively repress target gene expression in cells. These results establish that SqrR is a sensor of H2S-derived reactive sulfur species that maintain sulfide homeostasis in this photosynthetic bacterium and reveal the mechanism of sulfide-dependent transcriptional derepression of genes involved in sulfide metabolism.
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