Experimental Data Snapshot

  • Resolution: 1.60 Å
  • R-Value Work: 0.183 
  • R-Value Observed: 0.183 

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Control of oxidation-reduction potentials in flavodoxin from Clostridium beijerinckii: the role of conformation changes.

Ludwig, M.L.Pattridge, K.A.Metzger, A.L.Dixon, M.M.Eren, M.Feng, Y.Swenson, R.P.

(1997) Biochemistry 36: 1259-1280

  • DOI: https://doi.org/10.1021/bi962180o
  • Primary Citation of Related Structures:  
    1FLA, 1FLD, 1FLN, 1FVX, 2FAX, 2FDX, 2FLV, 2FOX, 2FVX, 3NLL, 4NLL, 4NUL, 5NLL, 5NUL, 5ULL, 6NUL

  • PubMed Abstract: 

    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.

  • Organizational Affiliation

    Department of Biological Chemistry, University of Michigan, Ann Arbor 48109-1055, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
FLAVODOXIN138Clostridium beijerinckiiMutation(s): 1 
Find proteins for P00322 (Clostridium beijerinckii)
Explore P00322 
Go to UniProtKB:  P00322
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP00322
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on FMN

Download Ideal Coordinates CCD File 
C17 H21 N4 O9 P
Experimental Data & Validation

Experimental Data

  • Resolution: 1.60 Å
  • R-Value Work: 0.183 
  • R-Value Observed: 0.183 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 60.88α = 90
b = 60.88β = 90
c = 69.79γ = 120
Software Package:
Software NamePurpose
X-PLORmodel building
SDMSdata reduction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1997-03-12
    Type: Initial release
  • Version 1.1: 2008-03-25
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2021-11-03
    Changes: Database references, Derived calculations, Other
  • Version 1.4: 2024-05-22
    Changes: Data collection