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PDBsum entry 2yam
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Oxidoreductase
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PDB id
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2yam
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References listed in PDB file
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Key reference
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Title
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X-Ray-Induced catalytic active-Site reduction of a multicopper oxidase: structural insights into the proton-Relay mechanism and o2-Reduction states.
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Authors
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H.Serrano-Posada,
S.Centeno-Leija,
S.P.Rojas-Trejo,
C.Rodríguez-Almazán,
V.Stojanoff,
E.Rudiño-Piñera.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 2015,
71,
2396-2411.
[DOI no: ]
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PubMed id
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Note: In the PDB file this reference is
annotated as "TO BE PUBLISHED". The citation details given above have
been manually determined.
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Abstract
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During X-ray data collection from a multicopper oxidase (MCO) crystal, electrons
and protons are mainly released into the system by the radiolysis of water
molecules, leading to the X-ray-induced reduction of O2 to 2H2O at the
trinuclear copper cluster (TNC) of the enzyme. In this work, 12 crystallographic
structures of Thermus thermophilus HB27 multicopper oxidase (Tth-MCO) in holo,
apo and Hg-bound forms and with different X-ray absorbed doses have been
determined. In holo Tth-MCO structures with four Cu atoms, the proton-donor
residue Glu451 involved in O2 reduction was found in a double conformation:
Glu451a (∼7 Å from the TNC) and Glu451b (∼4.5 Å from the TNC). A
positive peak of electron density above 3.5σ in an Fo - Fc map for
Glu451a O(ℇ2) indicates the presence of a carboxyl functional group at the
side chain, while its significant absence in Glu451b strongly suggests a
carboxylate functional group. In contrast, for apo Tth-MCO and in Hg-bound
structures neither the positive peak nor double conformations were observed.
Together, these observations provide the first structural evidence for a
proton-relay mechanism in the MCO family and also support previous studies
indicating that Asp106 does not provide protons for this mechanism. In addition,
eight composite structures (Tth-MCO-C1-8) with different X-ray-absorbed doses
allowed the observation of different O2-reduction states, and a total depletion
of T2Cu at doses higher than 0.2 MGy showed the high susceptibility of this Cu
atom to radiation damage, highlighting the importance of taking radiation
effects into account in biochemical interpretations of an MCO structure.
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