1JA8

Kinetic Analysis of Product Inhibition in Human Manganese Superoxide Dismutase


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.12 Å
  • R-Value Free: 0.284 
  • R-Value Work: 0.243 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Kinetic analysis of product inhibition in human manganese superoxide dismutase.

Hearn, A.S.Stroupe, M.E.Cabelli, D.E.Lepock, J.R.Tainer, J.A.Nick, H.S.Silverman, D.N.

(2001) Biochemistry 40: 12051-12058


  • PubMed Abstract: 
  • Manganese superoxide dismutase (MnSOD) cycles between the Mn(II) and Mn(III) states during the catalyzed disproportionation of O(2)(*-), a catalysis that is limited at micromolar levels of superoxide by a peroxide-inhibited complex with the metal. We ...

    Manganese superoxide dismutase (MnSOD) cycles between the Mn(II) and Mn(III) states during the catalyzed disproportionation of O(2)(*-), a catalysis that is limited at micromolar levels of superoxide by a peroxide-inhibited complex with the metal. We have investigated the role in catalysis and inhibition of the conserved residue Trp161 which forms a hydrophobic side of the active site cavity of MnSOD. Crystal structures of mutants of human MnSOD in which Trp161 was replaced with Ala or Phe showed significant conformational changes on adjacent residues near the active site, particularly Gln143 and Tyr34 which in wild-type MnSOD participate in a hydrogen bond network believed to support proton transfer during catalysis. Using pulse radiolysis and observing the UV absorbance of superoxide, we have determined rate constants for the catalytic dismutation of superoxide. In addition, the rates of formation and dissociation of the product-inhibited complex of these mutants were determined by direct observation of the characteristic visible absorption of the oxidized and inhibited states. Catalysis by W161A and W161F MnSOD was associated with a decrease of at least 100-fold in the catalytic rate of reduction of superoxide, which then promotes a competing pathway leading to product inhibition. The structural changes caused by the mutations at position 161 led to small changes, at most a 6-fold decrease, in the rate constant for formation of the inhibited complex. Solvent hydrogen isotope effects support a mechanism in which formation of this complex, presumably the peroxide dianion bound to the manganese, involves no rate-contributing proton transfer; however, the dissociation of the complex requires proton transfer to generate HO(2)(-) or H2O2.


    Organizational Affiliation

    Department of Pharmacology, University of Florida, Gainesville, Florida 32610, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Manganese Superoxide Dismutase
A, B
198Homo sapiensMutation(s): 1 
Gene Names: SOD2
EC: 1.15.1.1
Find proteins for P04179 (Homo sapiens)
Go to Gene View: SOD2
Go to UniProtKB:  P04179
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
MN
Query on MN

Download SDF File 
Download CCD File 
A, B
MANGANESE (II) ION
Mn
WAEMQWOKJMHJLA-UHFFFAOYSA-N
 Ligand Interaction
SO4
Query on SO4

Download SDF File 
Download CCD File 
A, B
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.12 Å
  • R-Value Free: 0.284 
  • R-Value Work: 0.243 
  • Space Group: P 61 2 2
Unit Cell:
Length (Å)Angle (°)
a = 79.608α = 90.00
b = 79.608β = 90.00
c = 240.101γ = 120.00
Software Package:
Software NamePurpose
CNSphasing
CNSrefinement
SCALEPACKdata scaling
DENZOdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2001-06-06
    Type: Initial release
  • Version 1.1: 2008-04-27
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Derived calculations, Version format compliance