Regulates the transcription of the copA and cueO genes. It detects cytoplasmic copper stress and activates transcription in response to increasing copper concentrations. Homodimer. It contains an N-terminal DNA binding region and a C-terminal metal binding region. Loss of Cu-induction of copA, forms smaller than wild-type colonies when grown on 2 mM CuSO(4) (PubMed:11167016). CueR tightly binds Cu(1+) via a linear S-Cu-S center.