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PDBsum entry 7fd1
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Electron transport
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PDB id
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7fd1
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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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Oxidized and reduced azotobacter vinelandii ferredoxin i at 1.4 a resolution: conformational change of surface residues without significant change in the [3fe-4s]+/0 cluster.
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Authors
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C.G.Schipke,
D.B.Goodin,
D.E.Mcree,
C.D.Stout.
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Ref.
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Biochemistry, 1999,
38,
8228-8239.
[DOI no: ]
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PubMed id
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Abstract
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The refined structure of reduced Azotobacter vinelandii 7Fe ferredoxin FdI at
100 K and 1.4 A resolution is reported, permitting comparison of [3Fe-4S]+ and
[3Fe-4S]0 clusters in the same protein at near atomic resolution. The reduced
state of the [3Fe-4S]0 cluster is established by single-crystal EPR following
data collection. Redundant structures are refined to establish the
reproducibility and accuracy of the results for both oxidation states. The
structure of the [4Fe-4S]2+ cluster in four independently determined FdI
structures is the same within the range of derived standard uncertainties,
providing an internal control on the experimental methods and the refinement
results. The structures of the [3Fe-4S]+ and [3Fe-4S]0 clusters are also the
same within experimental error, indicating that the protein may be enforcing an
entatic state upon this cluster, facilitating electron-transfer reactions. The
structure of the FdI [3Fe-4S]0 cluster allows direct comparison with the
structure of a well-characterized [Fe3S4]0 synthetic analogue compound. The
[3Fe-4S]0 cluster displays significant distortions with respect to the [Fe3S4]0
analogue, further suggesting that the observed [3Fe-4S]+/0 geometry in FdI may
represent an entatic state. Comparison of oxidized and reduced FdI reveals
conformational changes at the protein surface in response to reduction of the
[3Fe-4S]+/0 cluster. The carboxyl group of Asp15 rotates approximately 90
degrees, Lys84, a residue hydrogen bonded to Asp15, adopts a single
conformation, and additional H2O molecules become ordered. These structural
changes imply a mechanism for H+ transfer to the [3Fe-4S]0 cluster in agreement
with electrochemical and spectroscopic results.
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