title: Physical evidence for substrate binding in preventing cyclooxygenase inactivation under nitrative stress.
abstract: Prostaglandin biosynthesis is catalyzed by two spatially and functionally distinct active sites in cyclooxygenase (COX) enzymes. Despite the crucial role of COXs in biology, molecular details regarding the function and regulation of these enzymes are incompletely defined. Reactive nitrogen species, formed during oxidative stress, produce modifications that alter COX functionalities and prostaglandin biosynthesis. We previously established that COX-1 undergoes selective nitration on Tyr385 via a mechanism that requires the presence of bound heme cofactor. As this is a critical residue for COX-1 catalysis, nitration at this site results in enzyme inactivation. We now show that occupancy of the COX-1 active site with substrate protects against Tyr385 nitration and redirects nitration to alternative Tyr residues on COX-1, preserving catalytic activity. This study reveals a novel role for the substrate in protecting COX-1 from inactivation by nitration in pathophysiological settings.
authors.affiliation: Department of Pathology, Weill Cornell Medical College of Cornell University, 1300 York Avenue, New York, New York 10065, USA. rsdeeb@med.cornell.edu
authors.forename: Ruba S
authors.initials: RS
authors.lastname: Deeb
authors.forename: Cynthia
authors.initials: C
authors.lastname: Cheung
authors.forename: Tal
authors.initials: T
authors.lastname: Nuriel
authors.forename: Brian D
authors.initials: BD
authors.lastname: Lamon
authors.forename: Rita K
authors.initials: RK
authors.lastname: Upmacis
authors.forename: Steven S
authors.initials: SS
authors.lastname: Gross
authors.forename: David P
authors.initials: DP
authors.lastname: Hajjar
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D020134:Catalytic Domain; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D051545:Cyclooxygenase 1 / Q000737:chemistry / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004563:Electrochemistry; D004789:Enzyme Activation / Q000187:drug effects; D006418:Heme / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D030421:Peroxynitrous Acid / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D051381:Rats; D013312:Stress, Physiological / Q000187:drug effects*; D013379:Substrate Specificity; D053719:Tandem Mass Spectrometry; D014443:Tyrosine
chemical_list: D016861:Cyclooxygenase Inhibitors; D030421:Peroxynitrous Acid; D016718:Arachidonic Acid; D014443:Tyrosine; D006418:Heme; D051545:Cyclooxygenase 1; D011451:Prostaglandin-Endoperoxide Synthases