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References listed in PDB file
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Key reference
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Title
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Control of oxidation-Reduction potentials in flavodoxin from clostridium beijerinckii: the role of conformation changes.
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Authors
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M.L.Ludwig,
K.A.Pattridge,
A.L.Metzger,
M.M.Dixon,
M.Eren,
Y.Feng,
R.P.Swenson.
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Ref.
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Biochemistry, 1997,
36,
1259-1280.
[DOI no: ]
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PubMed id
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Abstract
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X-ray analyses of wild-type and mutant flavodoxins from Clostridium beijerinckii
show that the conformation of the peptide Gly57-Asp58, in a bend near the
isoalloxazine ring of FMN, is correlated with the oxidation state of the FMN
prosthetic group. The Gly-Asp peptide may adopt any of three conformations:
trans O-up, in which the carbonyl oxygen of Gly57 (O57) points toward the flavin
ring; trans O-down, in which O57 points away from the flavin; and cis O-down.
Interconversions among these conformers that are linked to oxidation-reduction
of the flavin can modulate the redox potentials of bound FMN. In the semiquinone
and reduced forms of the protein, the Gly57-Asp58 peptide adopts the trans O-up
conformation and accepts a hydrogen bond from the flavin N5H [Smith, W. W.,
Burnett, R. M., Darling, G. D., & Ludwig, M. L. (1977) J. Mol. Biol. 117,
195-225; Ludwig, M. L., & Luschinsky, C. L. (1992) in Chemistry and
Biochemistry of Flavoenzymes III (Müller, F., Ed.) pp 427-466, CRC Press, Boca
Raton, FL]. Analyses reported in this paper confirm that, in crystals of
wild-type oxidized C. beijerinckii flavodoxin, the Gly57-Asp58 peptide adopts
the O-down orientation and isomerizes to the cis conformation. This cis form is
preferentially stabilized in the crystals by intermolecular hydrogen bonding to
Asn137. Structures for the mutant Asn137Ala indicate that a mixture of all three
conformers, mostly O-down, exists in oxidized C. beijerinckii flavodoxin in the
absence of intermolecular hydrogen bonds. Redox potentials have been manipulated
by substitutions that alter the conformational energies of the bend at
56M-G-D-E. The mutation Asp58Pro was constructed to study a case where energies
for cis-trans conversion would be different from that of wild type.
Intermolecular interactions with Asn137 are precluded in the crystal, yet
Gly57-Pro58 is cis, and O-down, when the flavin is oxidized. Reduction of the
flavin induces rearrangement to the trans O-up conformation. Redox potential
shifts reflect the altered energies associated with the peptide rearrangement;
E(ox/sq) decreases by approximately 60 mV (1.3 kcal/mol). Further, the results
of mutation of Gly57 agree with predictions that a side chain at residue 57
should make addition of the first electron more difficult, by raising the energy
of the O-up conformer that forms when the flavin is reduced to its semiquinone
state. The ox/sq potentials in the mutants Gly57Ala, Gly57Asn, and Gly57Asp are
all decreased by approximately 60 mV (1.3 kcal/mol). Introduction of the
beta-branched threonine side chain at position 57 has much larger effects on the
conformations and potentials. The Thr57-Asp58 peptide adopts a trans O-down
conformation when the flavin is oxidized; upon reduction to the semiquinone, the
57-58 peptide rotates to a trans O-up conformation resembling that found in the
wild-type protein. Changes in FMN-protein interactions and in conformational
equilibria in G57T combine to decrease the redox potential for the ox/sq
equilibrium by 180 mV (+4.0 kcal/mol) and to increase the sq/hq potential by 80
mV (-1.7 kcal/mol). A thermodynamic scheme is introduced as a framework for
rationalizing the properties of wild-type flavodoxin and the effects of the
mutations.
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Secondary reference #1
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Title
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Cis-Trans isomerization of the 57-58 peptide in crystalline flavodoxins from c. Beijerinckii
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Authors
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M.L.Ludwig,
M.M.Dixon,
K.A.Pattridge,
R.P.Swenson.
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Ref.
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flavins and flavoproteins ...
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Secondary reference #2
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Title
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Structure and redox properties of clostridial flavodoxin
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Authors
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M.L.Ludwig,
C.L.Luschinsky.
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Ref.
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chemistry and biochemistry, 1992,
3,
427.
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Secondary reference #3
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Title
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Structural characterization of site mutants of clostridial flavodoxin
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Authors
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M.L.Ludwig,
K.A.Pattridge,
M.Eren,
R.P.Swenson.
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Ref.
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flavins and flavoproteins ...
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Secondary reference #4
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Title
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Structure and oxidation-Reduction behavior of 1-Deaza-Fmn flavodoxins: modulation of redox potentials in flavodoxins.
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Authors
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M.L.Ludwig,
L.M.Schopfer,
A.L.Metzger,
K.A.Pattridge,
V.Massey.
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Ref.
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Biochemistry, 1990,
29,
10364-10375.
[DOI no: ]
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PubMed id
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Secondary reference #5
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Title
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Structure of the semiquinone form of flavodoxin from clostridum mp. Extension of 1.8 a resolution and some comparisons with the oxidized state.
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Authors
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W.W.Smith,
R.M.Burnett,
G.D.Darling,
M.L.Ludwig.
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Ref.
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J Mol Biol, 1977,
117,
195-225.
[DOI no: ]
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PubMed id
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Figure 9.
FIG. 9. Interpretation of electron density corresponding to FMN in+flavodoxin semiquinone.
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Figure 13.
PIG. 13. The prrdominentj electronic struct,ure of neutral isoalloxazinc semiquinone (Miiller
et cd., 1970).
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The above figures are
reproduced from the cited reference
with permission from Elsevier
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Secondary reference #6
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Title
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The structure of clostridium mp flavodoxin as a function of oxidation state, Some comparisons of the fmn-Binding sites in oxidized, Semiquinone and reduced forms
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Authors
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M.L.Ludwig,
R.M.Burnett,
G.D.Darling,
S.R.Jordan,
D.S.Kendall,
W.W.Smith.
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Ref.
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flavins and flavoproteins : ...
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Secondary reference #7
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Title
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The structure of the oxidized form of clostridial flavodoxin at 1.9-A resolution.
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Authors
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R.M.Burnett,
G.D.Darling,
D.S.Kendall,
M.E.Lequesne,
S.G.Mayhew,
W.W.Smith,
M.L.Ludwig.
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Ref.
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J Biol Chem, 1974,
249,
4383-4392.
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PubMed id
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Secondary reference #8
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Title
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Structure of the radical form of clostridial flavodoxin: a new molecular model.
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Authors
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R.D.Andersen,
P.A.Apgar,
R.M.Burnett,
G.D.Darling,
M.E.Lequesne,
S.G.Mayhew,
M.L.Ludwig.
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Ref.
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Proc Natl Acad Sci U S A, 1972,
69,
3189-3191.
[DOI no: ]
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PubMed id
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Secondary reference #9
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Title
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The structure of a clostridial flavodoxin. I. Crystallographic characterization of the oxidized and semiquinone forms.
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Authors
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M.L.Ludwig,
R.D.Andersen,
S.G.Mayhew,
V.Massey.
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Ref.
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J Biol Chem, 1969,
244,
6047-6048.
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PubMed id
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