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PDBsum entry 1oc9
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Electron transport
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PDB id
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1oc9
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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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Tryparedoxins from crithidia fasciculata and trypanosoma brucei: photoreduction of the redox disulfide using synchrotron radiation and evidence for a conformational switch implicated in function.
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Authors
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M.S.Alphey,
M.Gabrielsen,
E.Micossi,
G.A.Leonard,
S.M.Mcsweeney,
R.B.Ravelli,
E.Tetaud,
A.H.Fairlamb,
C.S.Bond,
W.N.Hunter.
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Ref.
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J Biol Chem, 2003,
278,
25919-25925.
[DOI no: ]
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PubMed id
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Abstract
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Tryparedoxin (TryX) is a member of the thioredoxin (TrX) fold family involved in
the regulation of oxidative stress in parasitic trypanosomatids. Like TrX, TryX
carries a characteristic Trp-Cys-Xaa-Xaa-Cys motif, which positions a
redox-active disulfide underneath a tryptophan lid. We report the structure of a
Crithidia fasciculata tryparedoxin isoform (CfTryX2) in two crystal forms and
compare them with structures determined previously. Efforts to chemically
generate crystals of reduced TryX1 were unsuccessful, and we carried out a novel
experiment to break the redox-active disulfide, formed between Cys-40 and
Cys-43, utilizing the intense x-radiation from a third generation synchrotron
undulator beamline. A time course study of the S-S bond cleavage is reported
with the structure of a TryX1 C43A mutant as the control. When freed from the
constraints of a disulfide link to Cys-43, Cys-40 pivots to become slightly more
solvent-accessible. In addition, we have determined the structure of Trypanosoma
brucei TryX, which, influenced by the molecular packing in the crystal lattice,
displays a significantly different orientation of the active site tryptophan
lid. This structural change may be of functional significance when TryX
interacts with tryparedoxin peroxidase, the final protein in the
trypanothione-dependent peroxidase pathway. Comparisons with chloroplast TrX and
its substrate fructose 1,6-bisphosphate phosphatase suggest that this movement
may represent a general feature of redox regulation in the trypanothione and
thioredoxin peroxidase pathways.
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Figure 2.
FIG. 2. The structure of tryparedoxin. a, a ribbon diagram
depicting the TryX fold, secondary structure assignment, and
location of the redox-active disulfide formed between Cys-40 and
Cys-43 (yellow sticks). Figs. 2a and 3, 4,5 were prepared with
MOLSCRIPT (39) and RASTER3D (40). In b, the amino acid sequence
of residues colored red are strictly conserved, and those
colored black are similar at scale 7 in the ALSCRIPT program
(41). The active site motif WCPPCR is marked with o .
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Figure 4.
FIG. 4. The CfTryX1 and CfTryXC43A structures. Stereoview
overlay of the active sites of native CfTryX1 (carbon atoms
colored green) and CfTryX1C43A (carbon atoms colored magenta),
showing the adjustment in position of Ser-36 and Tyr-80 to
compensate for the mutation of Cys-43. Dashed lines represent
hydrogen bonding interactions.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2003,
278,
25919-25925)
copyright 2003.
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