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 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history


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: 10.1021/bi7005543
  • Structures With Same Primary Citation

  • 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 p ...

    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: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Cytochrome b2
A, B
511Saccharomyces cerevisiaeMutation(s): 1 
Gene Names: CYB2
EC: 1.1.2.3
Find proteins for P00175 (Saccharomyces cerevisiae (strain ATCC 204508 / S288c))
Go to UniProtKB:  P00175
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
HEM
Query on HEM

Download CCD File 
A
PROTOPORPHYRIN IX CONTAINING FE
C34 H32 Fe N4 O4
KABFMIBPWCXCRK-RGGAHWMASA-L
 Ligand Interaction
FMN
Query on FMN

Download CCD File 
A, B
FLAVIN MONONUCLEOTIDE
C17 H21 N4 O9 P
FVTCRASFADXXNN-SCRDCRAPSA-N
 Ligand Interaction
PYR
Query on PYR

Download CCD File 
B
PYRUVIC ACID
C3 H4 O3
LCTONWCANYUPML-UHFFFAOYSA-N
 Ligand Interaction
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

View Full Validation Report



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2007-09-11
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance