An ArsR-type transcriptional regulator, SoxR, regulates sulfur oxidization (Sox) system in Cupriavidus pinatubonensis JMP134

Abstract Thiosulfate serves as a critical intermediate in the sulfur biogeochemical cycle and is frequently oxidized by the sulfur oxidation (Sox) system to sulfate in bacteria. Cupriavidus pinatubonensis JMP134 employs a complete Sox system to oxidize S2O3 2– to SO4 2−, yet the regulatory mechanisms underlying this process remain unclear. A regulator gene located adjacent to the sox genes cluster encodes an ArsR-type transcriptional regulator (SoxR). Here we report the regulation of the sox genes by SoxR in C. pinatubonensis JMP134. The sox genes are transcribed as an operon from a promoter in the front of soxR. SoxR binds to DNA 23-bp downstream of the transcription start site, blocking the sox transcription. We present evidence that SoxR does not directly respond to S2O3 2– but instead reacts with reactive sulfane sulfur via Cys43 and Cys98, and this interaction is contingent upon a functional Sox system. These findings will deepen our understanding of the regulation of the Sox system in bacteria.