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PDBsum entry 1rd2
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Ribonucleic acid
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PDB id
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1rd2
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References listed in PDB file
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Key reference
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Title
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Multiple wavelength anomalous diffraction (mad) crystal structure of rusticyanin: a highly oxidizing cupredoxin with extreme acid stability.
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Authors
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R.L.Walter,
S.E.Ealick,
A.M.Friedman,
R.C.Blake,
P.Proctor,
M.Shoham.
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Ref.
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J Mol Biol, 1996,
263,
730-751.
[DOI no: ]
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PubMed id
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Abstract
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The X-ray crystal structure of the oxidized form of the extremely stable and
highly oxidizing cupredoxin rusticyanin from Thiobacillus ferrooxidans has been
determined by the method of multiwavelength anomalous diffraction (MAD) and
refined to 1.9 A resolution. Like other cupredoxins, rusticyanin is a
copper-containing metalloprotein, which is composed of a core beta-sandwich
fold. In rusticyanin the beta-sandwich is composed of a six- and a
seven-stranded beta-sheet. Also like other cupredoxins, the copper ion is
coordinated by a cluster of four conserved residues (His85, Cys138, His143,
Met148) arranged in a distorted tetrahedron. Rusticyanin has a redox potential
of 680 mV, roughly twice that of any other cupredoxin, and it is optimally
active at pH values < or = 2. By comparison with other cupredoxins, the
three-dimensional structure of rusticyanin reveals several possible sources of
the chemical differences, including more ordered secondary structure and more
intersheet connectivity than other cupredoxins. The acid stability and redox
potential of rusticyanin may also be enhanced over other cupredoxins by a more
extensive internal hydrogen bonding network and by more extensive hydrophobic
interactions surrounding the copper binding site. Finally, reduction in the
number of charged residues surrounding the active site may also make a major
contribution to acid stability. We propose that the resulting rigid copper
binding site, which is constrained by the surrounding hydrophobic environment,
structurally and electronically favours Cu(I). We propose that the two extreme
chemical properties of rusticyanin are interrelated; the same unique structural
features that enhance acid stability also lead to elevated redox potential.
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Figure 3.
Figure 3. The b-bulge connection
between sheets one and two in
rusticyanin. The indole ring of Trp7
from strand one inserts into the
bulge formed by Gly110, Phe111,
Ser112, and Pro113 from strand
10. It is anchored by both polar
and hydrophobic interactions.
The Figure was prepared using
MOLSCRIPT (Kraulis, 1991).
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Figure 8.
Figure 8. Stereoview of the hydrogen bonding network surrounding the partially buried residue Asp88. This network
provides stability between strands 9, 10 and 12 as well as helping to fix the orientation of the side-chain of Cys138.
The fourth copper ligand, Met148, has been omitted from this Figure for the sake of clarity.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(1996,
263,
730-751)
copyright 1996.
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