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PDBsum entry 1cc3
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Electron transport
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PDB id
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1cc3
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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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Structural basis of electron transfer modulation in the purple cua center.
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Authors
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H.Robinson,
M.C.Ang,
Y.G.Gao,
M.T.Hay,
Y.Lu,
A.H.Wang.
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Ref.
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Biochemistry, 1999,
38,
5677-5683.
[DOI no: ]
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PubMed id
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Abstract
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The X-ray structure of an engineered purple CuA center in azurin from
Pseudomonas aeruginosa has been determined and refined at 1.65 A resolution. Two
independent purple CuA azurin molecules are in the asymmetric unit of a new P21
crystal, and they have nearly identical conformations (rmsd of 0.27 A for
backbone atoms). The purple CuA azurin was produced by the loop-engineering
strategy, and the resulting overall structure is unperturbed. The insertion of a
slightly larger Cu-binding loop into azurin causes the two structural domains of
azurin to move away from each other. The high-resolution structure reveals the
detailed environment of the delocalized mixed-valence [Cu(1.5).Cu(1.5)]
binuclear purple CuA center, which serves as a useful reference model for other
native proteins, and provides a firm basis for understanding results from
spectroscopic and functional studies of this class of copper center in biology.
The two independent Cu-Cu distances of 2.42 and 2.35 A (with respective
concomitant adjustments of ligand-Cu distances) are consistent with that (2.39
A) obtained from X-ray absorption spectroscopy with the same molecule, and are
among the shortest Cu-Cu bonds observed to date in proteins or inorganic
complexes. A comparison of the purple CuA azurin structure with those of other
CuA centers reveals an important relationship between the angular position of
the two His imidazole rings with respect to the Cu2S2(Cys) core plane and the
distance between the Cu and the axial ligand. This relationship strongly
suggests that the fine structural variation of different CuA centers can be
correlated with the angular positions of the two histidine rings because, from
these positions, one can predict the relative axial ligand interactions, which
are responsible for modulating the Cu-Cu distance and the electron transfer
properties of the CuA centers.
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