Copper-sensitive repressor that has a key role in copper homeostasis. It is part of the cso operon involved in the cellular response to increasing concentrations of copper inside the bacterium, which can be highly toxic. In the presence of copper, CsoR fully dissociates from the promoter in the cso operon, leading to the transcription of its genes. Binds to a GC-rich pseudopallindromic sequence, 5'-GTAGCCCACCCCCAGTGGGGTGGGA-3', in the cso promoter region. Homodimer. Highly up-regulated during the early stages of invasion of the human blood-brain barrier. This protein has an antiparallel four-helix bundle architecture that represents a novel DNA-binding fold. Belongs to the CsoR family.