Crystallographic studies with xenon and nitrous oxide provide evidence for protein-dependent processes in the mechanisms of general anesthesia.

Background: The mechanisms by which general anesthetics, including xenon and nitrous oxide, act are only beginning to be discovered. However, structural approaches revealed weak but specific protein-gas interactions.

Methods: To improve knowledge, we performed x-ray crystallography studies under xenon and nitrous oxide pressure in a series of 10 binding sites within four proteins.

Pressure-response analysis of anesthetic gases xenon and nitrous oxide on urate oxidase: a crystallographic study.

The remarkably safe anesthetics xenon (Xe) and, to lesser extent, nitrous oxide (N(2)O) possess neuroprotective properties in preclinical studies. To investigate the mechanisms of pharmacological action of these gases, which are still poorly known, we performed both crystallography under a large range of gas pressure and biochemical studies on urate oxidase, a prototype of globular gas-binding proteins whose activity is modulated by inert gases. We show that Xe and N(2)O bind to, compete for, and expand the volume of a hydrophobic cavity located just behind the active site of urate oxidase and further inhibit urate oxidase enzymatic activity.

Structure-function perturbation and dissociation of tetrameric urate oxidase by high hydrostatic pressure.

Structure-function relationships in the tetrameric enzyme urate oxidase were investigated using pressure perturbation. As the active sites are located at the interfaces between monomers, enzyme activity is directly related to the integrity of the tetramer. The effect of hydrostatic pressure on the enzyme was investigated by x-ray crystallography, small-angle x-ray scattering, and fluorescence spectroscopy.

Oxygen pressurized X-ray crystallography: probing the dioxygen binding site in cofactorless urate oxidase and implications for its catalytic mechanism.

The localization of dioxygen sites in oxygen-binding proteins is a nontrivial experimental task and is often suggested through indirect methods such as using xenon or halide anions as oxygen probes. In this study, a straightforward method based on x-ray crystallography under high pressure of pure oxygen has been developed. An application is given on urate oxidase (UOX), a cofactorless enzyme that catalyzes the oxidation of uric acid to 5-hydroxyisourate in the presence of dioxygen.