PDBsum entry 1df1

Oxidoreductase

PDB id: 1df1

Contents

Protein chains

420 a.a. *

Ligands

HEM ×2

H4B ×2

ITU ×2

Metals

_ZN ×2

Waters ×218

* Residue conservation analysis

PDB id:

1df1

Name:

Oxidoreductase

Title:

Murine inosoxy dimer with isothiourea bound in the active site

Structure:

Nitric oxide synthase. Chain: a, b. Synonym: nos. Engineered: yes

Source:

Mus musculus. House mouse. Organism_taxid: 10090. Cell: macrophage. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PDB file)

Resolution:

2.35Å R-factor: 0.223 R-free: 0.298

Authors:

B.R.Crane,R.J.Rosenfeld,A.S.Arvai,D.K.Ghosh,S.Ghosh,J.A.Tainer, D.J.Stuehr,E.D.Getzoff

Key ref:

B.R.Crane et al. (1999). N-terminal domain swapping and metal ion binding in nitric oxide synthase dimerization. EMBO J, 18, 6271-6281. PubMed id: 10562539 DOI: 10.1093/emboj/18.22.6271

Date:

16-Nov-99 Release date: 08-Dec-99

Protein chains

P29477  (NOS2_MOUSE) -  Nitric oxide synthase, inducible from Mus musculus

Seq: 1144 a.a.

Struc: 420 a.a.

Enzyme reactions

• Enzyme class: E.C.1.14.13.39 - nitric-oxide synthase (NADPH).
• Reaction: 2 L-arginine + 3 NADPH + 4 O2 + H⁺ = 2 L-citrulline + 2 nitric oxide + 3 NADP⁺ + 4 H2O

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1093/emboj/18.22.6271

EMBO J 18:6271-6281 (1999)

PubMed id: 10562539

N-terminal domain swapping and metal ion binding in nitric oxide synthase dimerization.

B.R.Crane, R.J.Rosenfeld, A.S.Arvai, D.K.Ghosh, S.Ghosh, J.A.Tainer, D.J.Stuehr, E.D.Getzoff.

ABSTRACT

Nitric oxide synthase oxygenase domains (NOS(ox)) must bind tetrahydrobiopterin and dimerize to be active. New crystallographic structures of inducible NOS(ox) reveal that conformational changes in a switch region (residues 103-111) preceding a pterin-binding segment exchange N-terminal beta-hairpin hooks between subunits of the dimer. N-terminal hooks interact primarily with their own subunits in the 'unswapped' structure, and two switch region cysteines (104 and 109) from each subunit ligate a single zinc ion at the dimer interface. N-terminal hooks rearrange from intra- to intersubunit interactions in the 'swapped structure', and Cys109 forms a self-symmetric disulfide bond across the dimer interface. Subunit association and activity are adversely affected by mutations in the N-terminal hook that disrupt interactions across the dimer interface only in the swapped structure. Residue conservation and electrostatic potential at the NOS(ox) molecular surface suggest likely interfaces outside the switch region for electron transfer from the NOS reductase domain. The correlation between three-dimensional domain swapping of the N-terminal hook and metal ion release with disulfide formation may impact inducible nitric oxide synthase (i)NOS stability and regulation in vivo.

Selected figure(s)

Figure 1.
Figure 1 The effect of domain swapping on the N-terminal hook conformation in iNOS[ox]. Ribbon representation of the iNOS[ox] dimer in swapped (A) and unswapped (B) conformations. N-terminal hook regions (cyan and orange) interact primarily with their own subunits (purple and red) in the unswapped conformation, but reach across to associate with the opposite subunit in the swapped conformation. Each heme (yellow bonds) is cupped in the inward-facing palm of the central webbed -sheet of the 'catcher's mitt' subunit fold. A self-symmetric disulfide bond (yellow, bottom center) links the two subunits in the swapped conformation (A). A single zinc ion (gray, bottom center) is bound between the two subunits at the base of the catcher's mitts in the unswapped conformation (B). Two molecules of H[4]B (yellow, center, on edge) are also bound at the interface and line the active-center channels leading to the hemes.

Figure 5.
Figure 5 Potential interaction surfaces of iNOS[ox]. (A and B) Electrostatic potential mapped onto the solvent-accessible molecular surface of the unswapped zinc-bound iNOS[ox] dimer. In the left orientation (A) (matching Figure 1), surface surrounding the exposed heme edge (Region 1) is surrounded by significant positive (blue) electrostatic potential (contoured at 3 kT/q; k = Boltzmann constant, T = temperature, q = 1 point charge), whereas the region surrounding the zinc site [(B), Region 2] (right view, rotated 90° about a horizontal axis) is neutral or negative (red). A pocket adjoining Region 1 and near the heme-ligating thiolate also has significant positive potential and residue conservation (Region 3). (C and D) Solvent-accessible surface of the iNOS[ox] dimer (one subunit red, the other subunit blue) color coded by residue conservation (paler to more saturated represents less conserved to more conserved), based on a group of NOS oxygenase domain sequences representative of known species and isozymes. Conservation of surface residues is most pronounced around the exposed heme edge (Region 1) and in a region proximal to the heme thiolate (Region 3), and is low around the zinc site (Region 2).

The above figures are reprinted from an Open Access publication published by Macmillan Publishers Ltd: EMBO J (1999, 18, 6271-6281) copyright 1999.

Figures were selected by an automated process.