Merck

Communication between the zinc and tetrahydrobiopterin binding sites in nitric oxide synthase.

Biochemistry (2014-05-14)
Georges Chreifi, Huiying Li, Craig R McInnes, Colin L Gibson, Colin J Suckling, Thomas L Poulos
RESUMO

The nitric oxide synthase (NOS) dimer is stabilized by a Zn(2+) ion coordinated to four symmetry-related Cys residues exactly along the dimer 2-fold axis. Each of the two essential tetrahydrobiopterin (H4B) molecules in the dimer interacts directly with the heme, and each H4B molecule is ~15 Å from the Zn(2+). We have determined the crystal structures of the bovine endothelial NOS dimer oxygenase domain bound to three different pterin analogues, which reveal an intimate structural communication between the H4B and Zn(2+) sites. The binding of one of these compounds, 6-acetyl-2-amino-7,7-dimethyl-7,8-dihydro-4(3H)-pteridinone (1), to the pterin site and Zn(2+) binding are mutually exclusive. Compound 1 both directly and indirectly disrupts hydrogen bonding between key residues in the Zn(2+) binding motif, resulting in destabilization of the dimer and a complete disruption of the Zn(2+) site. Addition of excess Zn(2+) stabilizes the Zn(2+) site at the expense of weakened binding of 1. The unique structural features of 1 that disrupt the dimer interface are extra methyl groups that extend into the dimer interface and force a slight opening of the dimer, thus resulting in disruption of the Zn(2+) site. These results illustrate a very delicate balance of forces and structure at the dimer interface that must be maintained to properly form the Zn(2+), pterin, and substrate binding sites.

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Sigma-Aldrich
Zinc, purum, powder
Sigma-Aldrich
Zinc, granular, 30-100 mesh, 99%
Sigma-Aldrich
Zinc, wire, diam. 1.0 mm, 99.995% trace metals basis
Sigma-Aldrich
Zinc, powder, <150 μm, 99.995% trace metals basis
Sigma-Aldrich
Zinc, mossy, ≥99%
Sigma-Aldrich
Zinc, foil, thickness 0.25 mm, 99.9% trace metals basis
Zinc, foil, 10mm disks, thickness 1.0mm, as rolled, 99.99+%
Zinc, foil, 15mm disks, thickness 0.5mm, as rolled, 99.99+%
Zinc, foil, 10mm disks, thickness 0.025mm, as rolled, 99.99+%
Zinc, foil, 15mm disks, thickness 0.075mm, as rolled, 99.95+%
Zinc, foil, 10mm disks, thickness 0.175mm, as rolled, 99.95+%
Zinc, foil, 1m coil, thickness 0.5mm, as rolled, 99.95+%
Zinc, foil, 10mm disks, thickness 0.005mm, 99.9%
Zinc, foil, 0.3m coil, thickness 0.25mm, as rolled, 99.95+%
Zinc, foil, 15mm disks, thickness 1.0mm, as rolled, 99.95+%
Zinc, foil, 15mm disks, thickness 0.15mm, as rolled, 99.95+%
Zinc, foil, 0.3m coil, thickness 0.075mm, as rolled, 99.95+%
Zinc, foil, 10mm disks, thickness 0.5mm, as rolled, 99.99+%
Zinc, foil, 50x50mm, thickness 0.5mm, as rolled, 99.99+%
Zinc, foil, 15mm disks, thickness 0.05mm, as rolled, 99.95+%
Zinc, foil, 10mm disks, thickness 0.125mm, as rolled, 99.99+%
Zinc, foil, 0.5m coil, thickness 0.1mm, as rolled, 99.95+%
Zinc, foil, 10mm disks, thickness 0.25mm, as rolled, 99.95+%
Zinc, foil, 0.5m coil, thickness 1.0mm, as rolled, 99.95+%
Zinc, foil, 50x50mm, thickness 0.35mm, as rolled, 99.95+%
Zinc, foil, 15mm disks, thickness 0.02mm, 99.9%
Zinc, foil, 150x150mm, thickness 1.0mm, as rolled, 99.99+%
Zinc, foil, 0.5m coil, thickness 1.5mm, as rolled, 99.95+%
Zinc, foil, 15mm disks, thickness 0.35mm, as rolled, 99.95+%
Zinc, foil, 10mm disks, thickness 0.01mm, 99.9%