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Search The CSA
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Catalytic Site Atlas

CSA LITERATURE entry for 1bib

E.C. namebiotin---[acetyl-CoA-carboxylase] ligase
SpeciesEscherichia coli (Bacteria)
E.C. Number (IntEnz) 6.3.4.15
CSA Homologues of 1bib
CSA Entries With UniProtID P06709
CSA Entries With EC Number 6.3.4.15
PDBe Entry 1bib
PDBSum Entry 1bib
MACiE Entry 1bib

Literature Report

IntroductionThe biotin operon repressor, biotin—[acetyl-CoA-carboxylase] ligase or BirA, is a 33.5-kDa protein. BirA is bifunctional, serving both as the biotin activating enzyme and as a transcriptional regulator. It catalyzes the formation of biotinyl-5'-adenylate(bio-5'-AMP) from biotin and ATP and transfers biotin to a specific lysine residue on the biotin carboxyl carrier protein, a subunit of acetyl-CoA carboxylase. Bio-5'-AMP is also the corepressor of BirA.
MechansimIn the first half reaction, Lys183 catalyzes the attack of an oxygen atom of the biotin carboxylate group on P-alpha of ATP to form bio-5'-AMP plus pyrophosphate. The charged transition state is stabilised by a number of arginine residues. Bio-5'-AMP remains bound in the active site and is quite stable.
In the presence of the correct apoprotein, apoBCCP, the nucleophilic amino group of the Lys122 to be modified attacks the mixed anhydride carbon atom, thus forming an amide bond between biotin and the lysine side chain with AMP as the other product. Again Lys183 of BirA acts to stabilise the charged transition state. Once the amide bond is formed, the biotin moiety remains attached throughout the lifetime of the protein.
Reaction

Catalytic Sites for 1bib

Annotated By Reference To The Literature - Site 1 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
ArgA118118macie:sideChainThe positive charge stabilises the negative charges of the phosphate group on ATP.
ArgA317317macie:sideChainThe positive charge stabilises the negative charges of the phosphate group on ATP.
LysA183183macie:sideChainThe positive charge stabilises the negative charges of BTN carboxylate group and phosphate group.

Literature References

Notes:Arg121 is also catalytic, having identical function to Arg118, but does not appear in the PDB used. It is present in a disordered loop which becomes ordered upon ATP or bio-5'-AMP binding
Wilson KP
Escherichia coli biotin holoenzyme synthetase/bio repressor crystal structure delineates the biotin- and DNA-binding domains.
Proc Natl Acad Sci U S A 1992 89 9257-9261
PubMed: 1409631
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