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PDBsum entry 1gao
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Electron transport
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PDB id
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1gao
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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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Azotobacter vinelandii ferredoxin i: a sequence and structure comparison approach to alteration of [4fe-4s]2+/+ reduction potential.
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Authors
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K.Chen,
Y.S.Jung,
C.A.Bonagura,
G.J.Tilley,
G.S.Prasad,
V.Sridhar,
F.A.Armstrong,
C.D.Stout,
B.K.Burgess.
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Ref.
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J Biol Chem, 2002,
277,
5603-5610.
[DOI no: ]
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PubMed id
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Abstract
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The reduction potential (E(0)') of the [4Fe-4S](2+/+) cluster of Azotobacter
vinelandii ferredoxin I (AvFdI) and related ferredoxins is approximately 200 mV
more negative than the corresponding clusters of Peptostreptococcus
asaccharolyticus ferredoxin and related ferredoxins. Previous studies have shown
that these differences in E(0)' do not result from the presence or absence of
negatively charged surface residues or in differences in the types of
hydrophobic residues found close to the [4Fe-4S](2+/+) clusters. Recently, a
third, quite distinct class of ferredoxins (represented by the structurally
characterized Chromatium vinosum ferredoxin) was shown to have a [4Fe-4S](2+/+)
cluster with a very negative E(0)' similar to that of AvFdI. The observation
that the sequences and structures surrounding the very negative E(0)' clusters
in quite dissimilar proteins were almost identical inspired the construction of
three additional mutations in the region of the [4Fe-4S](2+/+) cluster of AvFdI.
The three mutations, V19E, P47S, and L44S, that incorporated residues found in
the higher E(0)' P. asaccharolyticus ferredoxin all led to increases in E(0)'
for a total of 130 mV with a 94-mV increase in the case of L44S. The results are
interpreted in terms of x-ray structures of the FdI variants and show that the
major determinant for the large increase in L44S is the introduction of an OH-S
bond between the introduced Ser side chain and the Sgamma atom of Cys ligand 42
and an accompanying movement of water.
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Figure 1.
Fig. 1. Comparison of the sequences near the low
potential [4Fe-4S]2+/+ clusters of three structurally
characterized ferredoxins: AvFdI (Protein Data Bank code 7FD1),
PaFd (Protein Data Bank code 1DUR), CvFd (Protein Data Bank code
1BLU), and AvFdIII. Amino acids in blue represent mutations
previously characterized (29). The amino acids in red represent
the residues of interest in this study. Cluster numbers refer to
the position of the cluster relative to the NH[2] terminus of
the protein.
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Figure 7.
Fig. 7. Details of the V19E AvFdI mutant structure and
comparison with native AvFdI and PaFd. A, superposition of
residues 19-21 and 42-47 of native AvFdI (green) and mutant
AvFdI (pink) with the corresponding [4Fe-4S] clusters. The root
mean square deviation between native and V19E AvFdI is 0.229
Å following least squares fit of all 526 main chain and C
 atoms. B,
superposition of residues 19-21 and 42-47 of native AvFdI
(green) and mutant AvFdI (blue), residues 17-19 and 39-44 of
PaFd (pink), and the corresponding [4Fe-4S] clusters. The V19E
mutation makes AvFdI like PaFd at this position. PaFd and native
AvFdI are superposed as in Fig. 2B, and the views are similar to
that shown in Fig. 2B.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2002,
277,
5603-5610)
copyright 2002.
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