PDBsum entry 2nse

Complex (oxidoreductase/peptide)

PDB id: 2nse

Contents

Protein chains

416 a.a. *

Ligands

CAC ×2

ARG ×2

HEM ×2

H4B ×2

GOL

Metals

_ZN

Waters ×261

* Residue conservation analysis

PDB id:

2nse

Name:

Complex (oxidoreductase/peptide)

Title:

Bovine endothelial nitric oxide synthase substrate complex

Structure:

Nitric oxide synthase. Chain: a, b. Fragment: heme domain. Engineered: yes

Source:

Bos taurus. Cattle. Organism_taxid: 9913. Cell: endothelial. Expressed in: escherichia coli bl21. Expression_system_taxid: 511693.

Biol. unit:

Dimer (from PDB file)

Resolution:

2.34Å R-factor: 0.216 R-free: 0.305

Authors:

C.S.Raman,H.Li,P.Martasek,V.Kral,B.S.S.Masters,T.L.Poulos

Key ref:

C.S.Raman et al. (1998). Crystal structure of constitutive endothelial nitric oxide synthase: a paradigm for pterin function involving a novel metal center. Cell, 95, 939-950. PubMed id: 9875848 DOI: 10.1016/S0092-8674(00)81718-3

Date:

13-Aug-98 Release date: 25-May-99

Protein chains

P29473  (NOS3_BOVIN) -  Nitric oxide synthase 3 from Bos taurus

Seq: 1205 a.a.

Struc: 416 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

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

2 × L-arginine + 3 × NADPH (Bound ligand (Het Group name = ARG) corresponds exactly) + 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: 10.1016/S0092-8674(00)81718-3

Cell 95:939-950 (1998)

PubMed id: 9875848

Crystal structure of constitutive endothelial nitric oxide synthase: a paradigm for pterin function involving a novel metal center.

C.S.Raman, H.Li, P.Martásek, V.Král, B.S.Masters, T.L.Poulos.

ABSTRACT

Nitric oxide, a key signaling molecule, is produced by a family of enzymes collectively called nitric oxide synthases (NOS). Here, we report the crystal structure of the heme domain of endothelial NOS in tetrahydrobiopterin (H4B)-free and -bound forms at 1.95 A and 1.9 A resolution, respectively. In both structures a zinc ion is tetrahedrally coordinated to pairs of symmetry-related cysteine residues at the dimer interface. The phylogenetically conserved Cys-(X)4-Cys motif and its strategic location establish a structural role for the metal center in maintaining the integrity of the H4B-binding site. The unexpected recognition of the substrate, L-arginine, at the H4B site indicates that this site is poised to stabilize a positively charged pterin ring and suggests a model involving a cationic pterin radical in the catalytic cycle.

Selected figure(s)

Figure 5.
Figure 5. Cooperativity and Molecular Mimicry in eNOS(A) Cross talk between H[4]B and L-Arg mediated by the heme propionate (Se-edge data). The guanidinium and amino groups of L-Arg are held in place by H-bonding with the conserved Glu-363. The amino group also H-bonds with a heme propionate. H[4]B H-bonds directly with the heme propionate, while the pteridine ring is sandwiched between Phe-462 in one monomer and Trp-449 in another, respectively.(B) L-Arg is a structural mimic of H[4]B at the pterin-binding site when SEITU is bound at the active site (-H[4]B, +SEITU data). L-Arg binds to the pterin site and exquisitely mimics the H[4]B interaction with eNOS ([A] and Figure 4). The specific interaction of the potent inhibitor, SEITU, at the active site is mediated by a pair of bifurcated H-bonds to Glu-363. Two water molecules bridge between the inhibitor and heme propionate. The ethyl group of the inhibitor forms nonbonded contacts with Val-338 and Phe-355. The ureido sulfur is positioned 3.5 Å and 4.0 Å above heme pyrrole B-ring nitrogen and the heme iron, respectively.

Figure 7.
Figure 7. Proposed Mechanism for Pterin in NO BiosynthesisThe uniqueness of the H[4]B–eNOS interaction (Figure 4) and the ability to bind L-Arg at the pterin site present a strong case for the involvement of a pterin radical in NOS catalysis and rule out the possibility of H[4]B ↔ qH[2]B cycling during NO biosynthesis. R represents the dihydroxypropyl side chain at the C6 position on the pterin ring.

The above figures are reprinted by permission from Cell Press: Cell (1998, 95, 939-950) copyright 1998.

Figures were selected by an automated process.