BirA (bifunctional biotin-[acetylCoA carboxylase] holoenzyme synthetase/ DNA-binding transcriptional repressor, bio-5'-AMP-binding) is a bifunctional protein that exhibits biotin ligase activity and also acts as the DNA binding transcriptional repressor of the biotin operon. Biotinyl-5'-AMP is the co-repressor and is also synthesized by BirA.
