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PDBsum entry 1bnc
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Fatty acid biosynthesis
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PDB id
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1bnc
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Three-Dimensional structure of the biotin carboxylase subunit of acetyl-Coa carboxylase.
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Authors
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G.L.Waldrop,
I.Rayment,
H.M.Holden.
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Ref.
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Biochemistry, 1994,
33,
10249-10256.
[DOI no: ]
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PubMed id
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Abstract
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Acetyl-CoA carboxylase is found in all animals, plants, and bacteria and
catalyzes the first committed step in fatty acid synthesis. It is a
multicomponent enzyme containing a biotin carboxylase activity, a biotin
carboxyl carrier protein, and a carboxyltransferase functionality. Here we
report the X-ray structure of the biotin carboxylase component from Escherichia
coli determined to 2.4-A resolution. The structure was solved by a combination
of multiple isomorphous replacement and electron density modification
procedures. The overall fold of the molecule may be described in terms of three
structural domains. The N-terminal region, formed by Met 1-Ile 103, adopts a
dinucleotide binding motif with five strands of parallel beta-sheet flanked on
either side by alpha-helices. The "B-domain" extends from the main body of the
subunit where it folds into two alpha-helical regions and three strands of
beta-sheet. Following the excursion into the B-domain, the polypeptide chain
folds back into the body of the protein where it forms an eight-stranded
antiparallel beta-sheet. In addition to this major secondary structural element,
the C-terminal domain also contains a smaller three-stranded antiparallel
beta-sheet and seven alpha-helices. The active site of the enzyme has been
identified tentatively by a difference Fourier map calculated between X-ray data
from the native crystals and from crystals soaked in a Ag+/biotin complex. Those
amino acid residues believed to form part of the active site pocket include His
209-Glu 211, His 236-Glu 241, Glu 276, Ile 287-Glu 296, and Arg 338.2+
represents the first X-ray model of a biotin-dependent carboxylase.
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