title: The structure of NS-398 bound to cyclooxygenase-2.
abstract: The cyclooxygenases (COX-1 and COX-2) are membrane-associated, heme-containing homodimers that generate prostaglandin H(2) from arachidonic acid (AA) in the committed step of prostaglandin biogenesis and are the targets for nonsteroidal anti-inflammatory drugs (NSAIDs). N-(2-cyclohexyloxy-4-nitrophenyl) methanesulfonamide (NS-398) was the first in a series of isoform-selective drugs designed to preferentially inhibit COX-2, with the aim of ameliorating many of the toxic gastrointestinal side effects caused by conventional NSAID inhibition. We determined the X-ray crystal structure of murine COX-2 in complex with NS-398 utilizing synchrotron radiation to 3.0A resolution. NS-398 binds in the cyclooxygenase channel in a conformation that is different than that observed for other COX-2-selective inhibitors, such as celecoxib, with no discernible penetration into the side pocket formed in COX-2 by the isoform-specific substitutions of I434V, H513R, and I523V. Instead, the methanesulfonamide moiety of NS-398 interacts with the side chain of Arg-120 at the opening of the cyclooxygenase channel, similar to that observed for acidic, nonselective NSAIDs such as indomethacin and flurbiprofen. Our structure validates inhibitor studies that identified Arg-120 as a molecular determinant for time-dependent inhibition of COX-2 by NS-398.
authors.affiliation: Hauptman-Woodward Medical Research Institute, The State University of New York at Buffalo, 700 Ellicott Street, Buffalo, NY 14203, USA.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Vecchio
authors.forename: Michael G
authors.initials: MG
authors.lastname: Malkowski
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D051546:Cyclooxygenase 2 / Q000737:chemistry*; D052246:Cyclooxygenase 2 Inhibitors / Q000737:chemistry*; D006860:Hydrogen Bonding; D051379:Mice; D008958:Models, Molecular; D009578:Nitrobenzenes / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013449:Sulfonamides / Q000737:chemistry*
chemical_list: D052246:Cyclooxygenase 2 Inhibitors; D009578:Nitrobenzenes; D013449:Sulfonamides; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2