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PDBsum entry 1a24
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Oxidoreductase
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PDB id
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1a24
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References listed in PDB file
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Key reference
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Title
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Structure of reduced dsba from escherichia coli in solution.
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Authors
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H.J.Schirra,
C.Renner,
M.Czisch,
M.Huber-Wunderlich,
T.A.Holak,
R.Glockshuber.
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Ref.
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Biochemistry, 1998,
37,
6263-6276.
[DOI no: ]
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PubMed id
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Abstract
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The three-dimensional structure of reduced DsbA from Escherichia coli in aqueous
solution has been determined by nuclear magnetic resonance (NMR) spectroscopy
and is compared with the crystal structure of oxidized DsbA [Guddat, L. W.,
Bardwell, J. C. A., Zander, T., and Martin, J. L. (1997) Protein Sci. 6,
1148-1156]. DsbA is a monomeric 21 kDa protein which consists of 189 residues
and is required for disulfide bond formation in the periplasm of E. coli. On the
basis of sequence-specific 1H NMR assignments, 1664 nuclear Overhauser
enhancement distance constraints, 118 hydrogen bond distance constraints, and
293 dihedral angle constraints were obtained as the input for the structure
calculations by simulated annealing with the program X-PLOR. The enzyme is made
up of two domains. The catalytic domain has a thioredoxin-like fold with a
five-stranded beta-sheet and three alpha-helices, and the second domain consists
of four alpha-helices and is inserted into the thioredoxin motif. The active
site between Cys30 and Cys33 is located at the N terminus of the first
alpha-helix in the thioredoxin-like domain. The solution structure of reduced
DsbA is rather similar to the crystal structure of the oxidized enzyme but
exhibits a different relative orientation of both domains. In addition, the
conformations of the active site and a loop between strand beta5 and helix
alpha7 are slightly different. These structural differences may reflect
important functional requirements in the reaction cycle of DsbA as they appear
to facilitate the release of oxidized polypeptides from reduced DsbA. The
extremely low pKa value of the nucleophilic active site thiol of Cys30 in
reduced DsbA is most likely caused by its interactions with the dipole of the
active site helix and the side chain of His32, as no other charged residues are
located next to the sulfur atom of Cys30 in the solution structure.
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