3DWJ

Heme-proximal W188H mutant of inducible nitric oxide synthase


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.75 Å
  • R-Value Free: 0.294 
  • R-Value Work: 0.226 

wwPDB Validation 3D Report Full Report


This is version 1.1 of the entry. See complete history

Literature

Stabilization and Characterization of a Heme-Oxy Reaction Intermediate in Inducible Nitric-oxide Synthase

Tejero, J.Biswas, A.Wang, Z.Q.Page, R.C.Haque, M.M.Hemann, C.Zweier, J.L.Misra, S.Stuehr, D.J.

(2008) J.Biol.Chem. 283: 33498-33507

  • DOI: 10.1074/jbc.M806122200

  • PubMed Abstract: 
  • Nitric-oxide synthases (NOS) are heme-thiolate enzymes that N-hydroxylate L-arginine (L-Arg) to make NO. NOS contain a unique Trp residue whose side chain stacks with the heme and hydrogen bonds with the heme thiolate. To understand its importance we ...

    Nitric-oxide synthases (NOS) are heme-thiolate enzymes that N-hydroxylate L-arginine (L-Arg) to make NO. NOS contain a unique Trp residue whose side chain stacks with the heme and hydrogen bonds with the heme thiolate. To understand its importance we substituted His for Trp188 in the inducible NOS oxygenase domain (iNOSoxy) and characterized enzyme spectral, thermodynamic, structural, kinetic, and catalytic properties. The W188H mutation had relatively small effects on l-Arg binding and on enzyme heme-CO and heme-NO absorbance spectra, but increased the heme midpoint potential by 88 mV relative to wild-type iNOSoxy, indicating it decreased heme-thiolate electronegativity. The protein crystal structure showed that the His188 imidazole still stacked with the heme and was positioned to hydrogen bond with the heme thiolate. Analysis of a single turnover L-Arg hydroxylation reaction revealed that a new heme species formed during the reaction. Its build up coincided kinetically with the disappearance of the enzyme heme-dioxy species and with the formation of a tetrahydrobiopterin (H4B) radical in the enzyme, whereas its subsequent disappearance coincided with the rate of l-Arg hydroxylation and formation of ferric enzyme. We conclude: (i) W188H iNOSoxy stabilizes a heme-oxy species that forms upon reduction of the heme-dioxy species by H4B. (ii) The W188H mutation hinders either the processing or reactivity of the heme-oxy species and makes these steps become rate-limiting for l-Arg hydroxylation. Thus, the conserved Trp residue in NOS may facilitate formation and/or reactivity of the ultimate hydroxylating species by tuning heme-thiolate electronegativity.


    Organizational Affiliation

    Department of Pathobiology, The Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Nitric oxide synthase, inducible
A, B
431Mus musculusGene Names: Nos2 (Inosl)
EC: 1.14.13.39
Find proteins for P29477 (Mus musculus)
Go to UniProtKB:  P29477
Small Molecules
Ligands 4 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
SO4
Query on SO4

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A
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
HEM
Query on HEM

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A, B
PROTOPORPHYRIN IX CONTAINING FE
HEME
C34 H32 Fe N4 O4
KABFMIBPWCXCRK-RGGAHWMASA-L
 Ligand Interaction
NH4
Query on NH4

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A, B
AMMONIUM ION
H4 N
QGZKDVFQNNGYKY-UHFFFAOYSA-O
 Ligand Interaction
H4B
Query on H4B

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Download CCD File 
A, B
5,6,7,8-TETRAHYDROBIOPTERIN
C9 H15 N5 O3
FNKQXYHWGSIFBK-RPDRRWSUSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.75 Å
  • R-Value Free: 0.294 
  • R-Value Work: 0.226 
  • Space Group: P 61 2 2
Unit Cell:
Length (Å)Angle (°)
a = 214.597α = 90.00
b = 214.597β = 90.00
c = 111.933γ = 120.00
Software Package:
Software NamePurpose
PHENIXrefinement
d*TREKdata reduction
PHENIXphasing
d*TREKdata scaling

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2008-09-30
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance