title: Binding of PDZ domains to the carboxy terminus of inducible nitric oxide synthase boosts electron transfer and NO synthesis.
abstract: iNOS lacks any phosphorylatable residue at its C-terminus despite displaying a 25-residue extension known to block electron transfer and activity. We report that C-terminal deletions of iNOS increased the cytochrome c reduction rate. Moreover, the interaction of the iNOS C-terminus with the PDZ domains of EBP50 or CAP70 resulted not only in augmented reductase activity and greater NO synthesis but also anticipated the formation of the air-stable semiquinone generated after NADPH addition. Hence, the C-terminus of iNOS regulates the activity of the enzyme, albeit, unlike nNOS and eNOS, displacement of the autoinhibitory element occurs upon binding to proteins with PDZ domains.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040, Spain.
authors.forename: Clara
authors.initials: C
authors.lastname: Aicart-Ramos
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040, Spain. Electronic address: jirodrig@quim.ucm.es.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Rodríguez-Crespo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016227:Benzoquinones / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D019556:COS Cells; D002522:Chlorocebus aethiops; D045304:Cytochromes c / Q000378:metabolism; D004138:Dinitrocresols / Q000378:metabolism; D004579:Electron Transport; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D009249:NADP / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D010750:Phosphoproteins; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D017923:Sodium-Hydrogen Exchangers; D013053:Spectrophotometry
chemical_list: D016227:Benzoquinones; D004138:Dinitrocresols; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C514896:PDZK1 protein, mouse; D010750:Phosphoproteins; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; C024132:4,6-dinitro-o-cresol; D009569:Nitric Oxide; C025232:semiquinone radicals; D009249:NADP; D045304:Cytochromes c; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse
keywords: Electron transfer; PDZ domain; Reductase; iNOS