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PDBsum entry 1r7h
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Electron transport
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PDB id
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1r7h
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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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Nrdh-Redoxin of corynebacterium ammoniagenes forms a domain-Swapped dimer.
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Authors
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M.Stehr,
Y.Lindqvist.
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Ref.
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Proteins, 2004,
55,
613-619.
[DOI no: ]
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PubMed id
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Abstract
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NrdH-redoxins constitute a family of small redox proteins, which contain a
conserved CXXC sequence motif, and are characterized by a glutaredoxin-like
amino acid sequence but a thioredoxin-like activity profile. Here we report the
structure of Corynebacterium ammoniagenes NrdH at 2.7 A resolution, determined
by molecular replacement using E. coli NrdH as model. The structure is the first
example of a domain-swapped dimer from the thioredoxin family. The
domain-swapped structure is formed by an inter-chain two-stranded anti-parallel
beta-sheet and is stabilized by electrostatic interactions at the dimer
interface. Size exclusion chromatography, and MALDI-ESI experiments revealed
however, that the protein exists as a monomer in solution. Similar to E. coli
NrdH-redoxin and thioredoxin, C. ammoniagenes NrdH-redoxin has a wide
hydrophobic pocket at the surface that could be involved in binding to
thioredoxin reductase. However, the loop between alpha2 and beta3, which is
complementary to a crevice in the reductase in the thioredoxin-thioredoxin
reductase complex, is the hinge for formation of the swapped dimer in C.
ammoniagenes NrdH-redoxin. C. ammoniagenes NrdH-redoxin has the highly conserved
sequence motif W61-S-G-F-R-P-[DE]67 which is unique to the NrdH-redoxins and
which determines the orientation of helix alpha3. An extended hydrogen-bond
network, similar to that in E. coli NrdH-redoxin, determines the conformation of
the loop formed by the conserved motif.
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Figure 1.
Figure 1. Schematic drawings of the three-dimensional structure
of C. ammoniagenes NrdH. The nomenclature of Martin (1995)[7]
was used for the helices and sheets and does not include the
 -sheet
of the dimer-interface. The redox active cysteine residues at
the N-terminal of helix  1
are shown as ball-and-stick models. A: Closed monomer. B: Open
monomer. C: Domain-swapped dimer, colored according to the
B-factors from light blue (20 Å^2) to red (45 Å^2)
as indicated on the reference bar. D: surface representation of
the domain-swapped dimer. The surface was calculated with
program MolMol[22] using a solvent radius of 1.4 Å and
colored according to the electrostatic potential, calculated
with the program  s
 simplecharge
 option.
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Figure 2.
Figure 2. Hydrogen-bond networks in the domain-swapped NrdH
dimer. A: The dimer interface. The -sheet
of the interface is formed by the residues 48-50 of both
domain-swapped monomers. The residues D37*, R40*, D40, and D41
of both 2
helices form a hydrogen-bond network. The molecule has the same
orientation as in Figure 1(A-D). B: View of the hydrogen-bond
network in the structure of C. ammonigenes NrdH formed by the
highly conserved WSGRFP sequence motif. Hydrogen bonds are drawn
as dashed lines.
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The above figures are
reprinted
by permission from John Wiley & Sons, Inc.:
Proteins
(2004,
55,
613-619)
copyright 2004.
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