<p>CopG, also known as RepA, is responsible for the regulation of plasmid copy number. It binds to the repAB promoter and controls synthesis of the plasmid replication initiator protein RepB. Many bacterial transcription regulation proteins bind DNA through a 'helix-turn-helix' motif, nevertheless CopG displays a fully defined HTH-motif structure that is involved not in DNA-binding, but in the maintenance of the intrinsic dimeric functional structure and cooperativity [<cite idref="PUB00004995"/>, <cite idref="PUB00001322"/>].</p>