Characterization of redox-active cysteine residues of persulfide-responsive transcriptional repressor SqrR. Issue 4 (4th July 2017)

• Record Type: Journal Article
• Authors: Shimizu, Takayuki; Masuda, Shinji
• Is Part Of: Communicative & integrative biology. Volume 10:Issue 4(2017)
• Publication Date: 2017-07-04
• Subjects: cysteine (Cys) -- hydrogen sulfide -- persulfide -- purple bacteria -- reactive sulfur species -- Rhodobacter -- SqrR -- sulfide sensor; Biology -- Periodicals; Molecular biology -- Periodicals; 579.05
• DOI: 10.1080/19420889.2017.1329786
• Languages: English
• ISSNs: 1942-0889

Abstract

ABSTRACT: We recently identified the novel persulfide sensor SqrR that functions as a master regulator of sulfide-dependent gene expression in the purple photosynthetic bacterium Rhodobacter capsulatus . SqrR binds to the promoter regions of target genes to repress their expression in the absence of sulfide, and the repressor activity is negated by sulfide treatment. SqrR has 3 cysteine residues, 2 of which are conserved in SqrR homologs from other bacteria: Cys41 and Cys107. SqrR forms an intramolecular tetrasulfide bond between Cys41 and Cys107 when exposed to persulfide, which results in loss of the DNA-binding activity in vitro . Here, we address the mechanism through which these cysteine residues are modified by persulfides. We show that the predicted p K a value of Cys107, as revealed by a putative SqrR structural model, is lower than that of Cys41. Furthermore, C41S SqrR in which Cys41 was changed to serine forms an intermolecular disulfide-bond between Cys107 of 2 SqrRs, suggesting high nucleophilic reactivity of Cy107. These data suggest that Cys107 and Cys41 function as attacking Cys and resolving Cys, respectively; this occurs during tetrasulfide-bond formation of WT SqrR, when it is exposed to persulfide.