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PDBsum entry 5b4j
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Oxidoreductase
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PDB id
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5b4j
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References listed in PDB file
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Key reference
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Title
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Atomic-Resolution structure of the phycocyanobilin:ferredoxin oxidoreductase i86d mutant in complex with fully protonated biliverdin.
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Authors
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Y.Hagiwara,
K.Wada,
T.Irikawa,
H.Sato,
M.Unno,
K.Yamamoto,
K.Fukuyama,
M.Sugishima.
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Ref.
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Febs Lett, 2016,
590,
3425-3434.
[DOI no: ]
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PubMed id
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Abstract
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Phycocyanobilin:ferredoxin oxidoreductase (PcyA) catalyzes the reduction of
biliverdin (BV) to produce phycocyanobilin, a linear tetrapyrrole pigment used
for light harvesting and light sensing. Spectroscopic and HPLC analyses
inidicate that BV bound to the I86D mutant of PcyA is fully protonated (BVH(+) )
and can accept an electron, but I86D is unable to donate protons for the
reduction; therefore, compared to the wild-type PcyA, the I86D mutant stabilizes
BVH(+) . To elucidate the structural basis of the I86D mutation, we determined
the atomic-resolution structure of the I86D-BVH(+) complex and the protonation
states of the essential residues Asp105 and Glu76 in PcyA. Our study revealed
that Asp105 adopted a fixed conformation in the I86D mutant, although it had
dual conformations in wild-type PcyA which reflected the protonation states of
BV. Taken together with biochemical/spectroscopic results, our analysis of the
I86D-BVH(+) structure supports the hypothesis that flexibility of Asp105 is
essential for the catalytic activity of PcyA.
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