The Copper Homeostasis Transcription Factor CopR Is Involved in HO Stress in CAUH2.

Transcriptional factors (TFs) play important roles in the responses to oxidative, acid, and other environmental stresses in Gram-positive bacteria, but the regulatory mechanism of TFs involved in oxidative stress remains unknown in lactic acid bacteria. In the present work, homologous overexpression strains with 43 TFs were constructed in the CAUH2 parent strain. The strain overexpressing CopR displayed the highest sensitivity and a 110-fold decrease in survival rate under HO challenge. The importance of CopR in the response to HO stress was further confirmed by a 10.8-fold increase in the survival of a insertion mutant. analysis of the genes flanking revealed putative CopR-binding " box" sequences in the promoter region of the adjacent gene encoding a Cu-exporting ATPase. Electrophoretic mobility shift assay (EMSA) analysis demonstrated the specific binding of CopR with , suggesting is a target gene of CopR in . The role of CopB involved in oxidative stress was verified by the significantly decreased survival in the mutant. Furthermore, a growth defect in copper-containing medium demonstrated that CopB functions as an export ATPase for copper ions. Furthermore, EMSAs revealed that CopR functions as a regulator that negatively regulates gene and Cu serves as inducer of CopR to activate the expression of CopB in response to HO stress in CAUH2. Our findings indicated that CopR plays an important role in enhancing oxidative resistance by regulating to modulate copper homeostasis.