Corynebacterium glutamicum CsoR Acts as a Transcriptional Repressor of Two Copper/Zinc-Inducible P1B-Type ATPase Operons

The mechanism of regulation of the expression of copA and copB, encoding putative copper-translocating P-1B-type ATPases in Corynebacterium glutamicum, was investigated. The levels of copA and .copB mRNAs were upregulated in response to excess copper as well as excess zinc. Disruption of csoR, encoding a transcriptional regulator, resulted in constitutive expression of copA and copB. The CsoR protein bound to the promoter regions of the copA-csoR and the cgR_0124-copB-cgR_0126 operon. In vitro DNA binding activity was strongly inhibited by copper, but much less inhibited by zinc. A csoR-deficient mutant showed slightly increased resistance to copper, but slightly decreased resistance to zinc. These findings indicate that CsoR acts as a transcriptional repressor not only of the cognate copA-csoR operon but also of the cgR_0124-copB-cgR_0126 operon, which is not physically linked to csoR on the chromosome, and that CsoR plays a major role in copper homeostasis.