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. Author manuscript; available in PMC: 2011 Jan 29.
Published in final edited form as: Chem Biol. 2010 Jan 29;17(1):11. doi: 10.1016/j.chembiol.2009.12.007

Figure 2.

Figure 2

The competing protein interactions model of the biotin operon regulatory switch and alignments of biotin-accepting sequences. (A) Shown are the regulatory effects engendered by differing levels of AccB expression. The symbols are as in Fig. 1. In the competing protein-protein interaction model a BirA:bio-AMP monomer is proposed to interact with AccB and thereby inhibit dimerization of the BirA:bio-AMP complex, the species required for DNA binding (Beckett, 2007). When the rate of AccB synthesis and demand for biotin decreases BirA:bio-AMP dimers accumulate and repress bio operon transcription. (B) Alignment of the residues neighboring the biotin attachment site (asterisk) of E. coli AccB and the five biotin acceptor proteins from species whose BPLs are reported to biotinylate E. coli AccB, but not peptide 85 fusion proteins. For comparison the sequences of peptides 85 and ME are also given. Residues conserved in at least four of the sequences are boxed. The natural sequences are: Ec, E. coli AccB; Bs, Bacillus subtilis AccB: Mj, Methanocaldococcus jannaschii pyruvate carboxylase; Sc, Saccharomyces cerevesiae pyruvate carboxylase 1; At, Arabidopsis thaliana AccB and Hs, Homo sapiens, pyruvate carboxylase. Note that the in the libraries that yielded the two peptide sequences of interest, the codons of the conserved alanine residue located two resides upstream of the biotinylated lysine together with the upstream and downstream glutamate residues were 97% enriched.