Crystal Structure of Constitutive Endothelial Nitric Oxide Synthase: A Paradigm for Pterin Function Involving a Novel Metal Center

• Published in: Cell Vol. 95; no. 7; pp. 939 - 950
• Main Authors: Raman, C.S, Li, Huiying, Martásek, Pavel, Král, Vladimir, Masters, Bettie Sue S, Poulos, Thomas L
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 23-12-1998
• Subjects: Amino Acid Sequence; Animals; Binding Sites; Biopterins - analogs & derivatives; Biopterins - metabolism; Catalysis; Cations - metabolism; Cattle; CRYSTAL STRUCTURE; Crystallization; Crystallography, X-Ray; Cysteine - metabolism; Dimerization; Heme - metabolism; Hydrogen Bonding; MATERIALS SCIENCE; Models, Molecular; Molecular Mimicry; NATIONAL SYNCHROTRON LIGHT SOURCE; NITRIC OXIDE; Nitric Oxide Synthase - chemistry; Nitric Oxide Synthase - metabolism; Nitric Oxide Synthase Type III; NSLS; Protein Structure, Secondary; PTERIDINES; Pterins - metabolism; Sequence Alignment; Zinc - metabolism
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/S0092-8674(00)81718-3

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 (H
4B)-free and -bound forms at 1.95 Å and 1.9 Å 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 H
4B-binding site. The unexpected recognition of the substrate, L-arginine, at the H
4B 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.