Sulfide-responsive transcriptional repressor SqrR functions as a master regulator of sulfide-dependent photosynthesis

Significance Hydrogen sulfide is a universal bioactive molecule that functions in both prokaryotes and eukaryotes. However, little is known about intra- and extracellular sulfide-sensing mechanisms. Here we show that the sulfide-regulated repressor SqrR from a purple bacterium forms an intramolecular tetrasulfide bond in response to sulfide stress in vivo and organic persulfides in vitro, revealing the importance of this cysteine modification...