Negative regulator of clpC, clpB and clpP transcription by binding directly and specifically to their promoter region. Interacts with McsA and McsB. Up-regulated by heavy metals such as Cu(2+) and Cd(2+), but Zn(2+) and Co(2+) have no effect. Forms part of an operon with mcsA, mcsB and clpC. Belongs to the CtsR family.