1BDO: Structure Of The Biotinyl Domain Of Acetyl-Coenzyme A Carboxylase Determined By Mad Phasing

BACKGROUND: Acetyl-coenzyme A carboxylase catalyzes the first committed step of fatty acid biosynthesis. Universally, this reaction involves three functional components all related to a carboxybiotinyl intermediate. A biotinyl domain shuttles its covalently attached biotin prosthetic group between the active sites of a biotin carboxylase and a carboxyl transferase. In Escherichia coli, the three components reside in separate subunits: a biotinyl domain is the functional portion of one of these, biotin carboxy carrier protein (BCCP). RESULTS: We have expressed natural and selenomethionyl (Se-met) BCCP from E. coli as biotinylated recombinant proteins, proteolyzed them with subtilisin Carlsberg to produce the biotinyl domains BCCP and Se-met BCCPsc, determined the crystal structure of Se-met BCCPsc using a modified version of the multiwavelength anomalous diffraction (MAD) phasing protocol, and refined the structure for the natural BCCPsc at 1.8 A resolution. The structure may be described as a capped beta sandwich with quasi-dyad symmetry. Each half contains a characteristic hammerhead motif. The biotinylated lysin is located at a hairpin beta turn which connects the two symmetric halves of the molecule, and its biotinyl group interacts with a non-symmetric protrusion from the core. CONCLUSIONS: This first crystal structure of a biotinyl domain helps to unravel the central role of such domains in reactions catalyzed by biotin-dependent carboxylases. The hammerhead structure observed twice in BCCPsc may be regarded as the basic structural motif of biotinyl and lipoyl domains of a superfamily of enzymes. The new MAD phasing techniques developed in the course of determining this structure enhance the power of the MAD method.
PDB ID: 1BDODownload
MMDB ID: 55492
PDB Deposition Date: 1995/11/21
Updated in MMDB: 2011/11
Experimental Method:
x-ray diffraction
Resolution: 1.8  Å
Source Organism:
Similar Structures:
Biological Unit for 1BDO: dimeric; determined by author
Molecular Components in 1BDO
Label Count Molecule
Proteins (2 molecules)
Acetyl-coa Carboxylase(Gene symbol: accB)
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB