Regulates the transcription of the copA and cuiD (cueO) genes. Detects cytoplasmic copper stress and activates transcription in response to increasing copper concentrations (PubMed:17768242). Homodimer. It contains a N-terminal DNA binding region and a C-terminal metal binding region. Loss of copper-based induction of copA. Causes a mild defect in aerobic growth on CuSO(4), strongly impairs survival during anaerobic growth on CuSO(4).