Role of nitri oxide-responsive repressor NsrR in global transcription control

This study investigates how Bacillus subtilis senses and responds to oxygen limitation, focusing on the NO-sensitive regulation of nitrate respiration genes by NsrR. NsrR, a [4Fe-4S] cluster protein, represses nasD transcription by disrupting nasD-ResD-RNA polymerase complexes. NO modifies NsrR via iron dinitrosylation, reducing its DNA-binding affinity. Two distinct NsrR-binding sites—class I and class II—were identified, with genome-wide analysis revealing a broader regulon under complex control by AbrB, Rok, Fur, and ResD. These findings provide mechanistic insight into NO-mediated transcriptional regulation and lay the foundation for understanding regulatory interplay during anaerobic adaptation.