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

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 S2O32- to SO42-, 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 S2O32- 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.