InterPro domain: IPR003142

This C-terminal domain has an SH3-like barrel fold, the function of which is unknown. It is found associated with prokaryotic bifunctional transcriptional repressors [ 1 ] and eukaryotic enzymes involved in biotin utilization [ 2 , 3 ].

In Escherichia coli the biotin operon repressor (BirA) is a bifunctional protein. BirA acts both as the acetyl-coA carboxylase biotin holoenzyme synthetase ( 6.3.4.15 ) and as the biotin operon repressor. DNA sequence analysis of mutations indicates that the helix-turn-helix DNA binding region is located at the N terminus while mutations affecting enzyme function, although mapping over a large region, are found mainly in the central part of the protein's primary sequence [ 4 ].

1. Crystallization of the bifunctional biotin operon repressor. J. Biol. Chem. 264, 5
2. Isolation and characterization of mutations in the human holocarboxylase synthetase cDNA. Nat. Genet. 8, 122-8
3. Evidence for multiple forms of biotin holocarboxylase synthetase in pea (Pisum sativum) and in Arabidopsis thaliana: subcellular fractionation studies and isolation of a cDNA clone. Biochem. J. 323 ( Pt 1), 179-88