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PDBsum entry 3itj
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Oxidoreductase
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PDB id
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3itj
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References listed in PDB file
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Key reference
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Title
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Insights into the specificity of thioredoxin reductase-Thioredoxin interactions. A structural and functional investigation of the yeast thioredoxin system.
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Authors
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M.A.Oliveira,
K.F.Discola,
S.V.Alves,
F.J.Medrano,
B.G.Guimarães,
L.E.Netto.
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Ref.
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Biochemistry, 2010,
49,
3317-3326.
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PubMed id
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Abstract
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The enzymatic activity of thioredoxin reductase enzymes is endowed by at least
two redox centers: a flavin and a dithiol/disulfide CXXC motif. The interaction
between thioredoxin reductase and thioredoxin is generally species-specific, but
the molecular aspects related to this phenomenon remain elusive. Here, we
investigated the yeast cytosolic thioredoxin system, which is composed of NADPH,
thioredoxin reductase (ScTrxR1), and thioredoxin 1 (ScTrx1) or thioredoxin 2
(ScTrx2). We showed that ScTrxR1 was able to efficiently reduce yeast
thioredoxins (mitochondrial and cytosolic) but failed to reduce the human and
Escherichia coli thioredoxin counterparts. To gain insights into this
specificity, the crystallographic structure of oxidized ScTrxR1 was solved at
2.4 A resolution. The protein topology of the redox centers indicated the
necessity of a large structural rearrangement for FAD and thioredoxin reduction
using NADPH. Therefore, we modeled a large structural rotation between the two
ScTrxR1 domains (based on the previously described crystal structure, PDB code
1F6M ). Employing diverse approaches including enzymatic assays, site-directed
mutagenesis, amino acid sequence alignment, and structure comparisons, insights
were obtained about the features involved in the species-specificity phenomenon,
such as complementary electronic parameters between the surfaces of ScTrxR1 and
yeast thioredoxin enzymes and loops and residues (such as Ser(72) in ScTrx2).
Finally, structural comparisons and amino acid alignments led us to propose a
new classification that includes a larger number of enzymes with thioredoxin
reductase activity, neglected in the low/high molecular weight classification.
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