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PDBsum entry 1c09
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Electron transport
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PDB id
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1c09
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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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Modulation of the redox potential of the [fe(scys)(4)] site in rubredoxin by the orientation of a peptide dipole.
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Authors
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M.K.Eidsness,
A.E.Burden,
K.A.Richie,
D.M.Kurtz,
R.A.Scott,
E.T.Smith,
T.Ichiye,
B.Beard,
T.Min,
C.Kang.
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Ref.
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Biochemistry, 1999,
38,
14803-14809.
[DOI no: ]
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PubMed id
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Abstract
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Rubredoxins (Rds) may be separated into two classes based upon the correlation
of their reduction potentials with the identity of residue 44; those with Ala44
have reduction potentials that are approximately 50 mV higher than those with
Val44. The smaller side chain volume occupied by Ala44 relative to that occupied
by Val44 has been proposed to explain the increase in the reduction potential,
based upon changes in the Gly43-Ala44 peptide bond orientation and the distance
to the [Fe(SCys)(4)] center in the Pyrococcus furiosus (Pf) Rd crystal structure
compared to those of Gly43-Val44 in the Clostridium pasteurianum (Cp) Rd crystal
structure. As an experimental test of this hypothesis, single-site Val44
<--> Ala44 exchange mutants, [V44A]Cp and [A44V]Pf Rds, have been cloned
and expressed. Reduction potentials of these residue 44 variants and pertinent
features of the X-ray crystal structure of [V44A]Cp Rd are reported. Relative to
those of wild-type Cp and Pf Rds, the V44A mutation in Cp Rd results in an 86 mV
increase in midpoint reduction potential and the [A44V] mutation in Pf Rd
results in a 95 mV decrease in midpoint reduction potential, respectively. In
the crystal structure of [V44A]Cp Rd, the peptide bond between residues 43 and
44 is approximately 0.3 A closer to the Fe center and the hydrogen bond distance
between the residue 44 peptide nitrogen and the Cys42 gamma-sulfur decreases by
0.32 A compared to the analogous distances in the wild-type Cp Rd crystal
structure. The results described herein support the prediction that the identity
of residue 44 alone determines whether a Rd reduction potential of about -50 or
0 mV is observed.
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