Bifunctional ligase/repressor BirA (BirA)

The E. coli protein-biotin ligase BirA is extremely specific and covalently attaches biotin to a single lysine in the endogenously expressed BCCP subunit of acetyl-CoA carboxylase2. Additionally, a small synthetic 15-amino-acid peptide is effectively biotinylated by BirA3,4 and fusion of the synthetic biotin acceptor peptide (AP) to a target protein creates an efficient approach for site-specific in vivo and in vitro biotinylation through co-expression or addition of BirA. Although the high specificity and activity of BirA towards the synthetic AP provide a powerful approach for specific labeling, the range of applications for BirA mediated biotinylation is restricted to samples containing AP-fused proteins.