Represses transcription of the class Ib RNR genes nrdHIEF but has much smaller effect on transcription of the class Ia RNR genes nrdAB and class III RNR genes nrdDG. By binding to nrdR boxes in the promoter regions to alter promoter activity, nrdR differentially regulates nrdAB, nrdHIEF and nrdD transcription in aerobic growth. Binds 1 zinc ion. Belongs to the NrdR family.