2OZ0

Mechanistic and Structural Studies of H373Q Flavocytochrome b2: Effects of Mutating the Active Site Base


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.80 Å
  • R-Value Free: 0.278 
  • R-Value Work: 0.206 
  • R-Value Observed: 0.210 

Starting Model: experimental
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Literature

Mechanistic and structural studies of H373Q flavocytochrome b2: effects of mutating the active site base.

Tsai, C.L.Gokulan, K.Sobrado, P.Sacchettini, J.C.Fitzpatrick, P.F.

(2007) Biochemistry 46: 7844-7851

  • DOI: https://doi.org/10.1021/bi7005543
  • Primary Citation of Related Structures:  
    2OZ0

  • PubMed Abstract: 

    His373 in flavocytochrome b2 has been proposed to act as an active site base during the oxidation of lactate to pyruvate, most likely by removing the lactate hydroxyl proton. The effects of mutating this residue to glutamine have been determined to provide further insight into its role. The kcat and kcat/Klactate values for the mutant protein are 3 to 4 orders of magnitude smaller than the wild-type values, consistent with a critical role for His373. Similar effects are seen when the mutation is incorporated into the isolated flavin domain of the enzyme, narrowing the effects to lactate oxidation rather than subsequent electron transfers. The decrease of 3500-fold in the rate constant for reduction of the enzyme-bound FMN by lactate confirms this part of the reaction as that most effected by the mutation. The primary deuterium and solvent kinetic isotope effects for the mutant enzyme are significantly smaller than the wild-type values, establishing that bond cleavage steps are less rate-limiting in H373Q flavocytochrome b2 than in the wild-type enzyme. The structure of the mutant enzyme with pyruvate bound, determined at 2.8 A, provides a rationale for these effects. The orientation of pyruvate in the active site is altered from that seen in the wild-type enzyme. In addition, the active site residues Arg289, Asp 292, and Leu 286 have altered positions in the mutant protein. The combination of an altered active site and the small kinetic isotope effects is consistent with the slowest step in turnover being a conformational change involving a conformation in which lactate is bound unproductively.


  • Organizational Affiliation

    Department of Chemistry, Texas A&M University, College Station, Texas 77843-2128, USA.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Cytochrome b2
A, B
511Saccharomyces cerevisiaeMutation(s): 1 
Gene Names: CYB2
EC: 1.1.2.3
UniProt
Find proteins for P00175 (Saccharomyces cerevisiae (strain ATCC 204508 / S288c))
Explore P00175 
Go to UniProtKB:  P00175
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP00175
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.80 Å
  • R-Value Free: 0.278 
  • R-Value Work: 0.206 
  • R-Value Observed: 0.210 
  • Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 163.689α = 90
b = 163.689β = 90
c = 112.021γ = 120
Software Package:
Software NamePurpose
REFMACrefinement
ADSCdata collection
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2007-09-11
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2021-10-20
    Changes: Database references, Derived calculations
  • Version 1.3: 2023-08-30
    Changes: Data collection, Refinement description
  • Version 2.0: 2023-11-15
    Changes: Atomic model, Data collection