title: Electron flow through nitrotyrosinate in Pseudomonas aeruginosa azurin.
abstract: We have designed ruthenium-modified Pseudomonas aeruginosa azurins that incorporate 3-nitrotyrosine (NO2YOH) between Ru(2,2'-bipyridine)2(imidazole)(histidine) and Cu redox centers in electron transfer (ET) pathways. We investigated the structures and reactivities of three different systems: RuH107NO2YOH109, RuH124NO2YOH122, and RuH126NO2YOH122. RuH107NO2YOH109, unlabeled H124NO2YOH122, and unlabeled H126NO2YOH122 were structurally characterized. The pKa's of NO2YOH at positions 122 and 109 are 7.2 and 6.0, respectively. Reduction potentials of 3-nitrotyrosinate (NO2YO(-))-modified azurins were estimated from cyclic and differential pulse voltammetry data: oxidation of NO2YO(-)122 occurs near 1.1 versus NHE; oxidation of NO2YO(-)109 is near 1.2 V. Our analysis of transient optical spectroscopic experiments indicates that hopping via NO2YO(-) enhances Cu(I) oxidation rates over single-step ET by factors of 32 (RuH107NO2YO(-)109), 46 (RuH126NO2YO(-)122), and 13 (RuH124NO2YO(-)122).
authors.affiliation: Beckman Institute and Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Warren
authors.forename: Nadia
authors.initials: N
authors.lastname: Herrera
authors.forename: Michael G
authors.initials: MG
authors.lastname: Hill
authors.forename: Jay R
authors.initials: JR
authors.lastname: Winkler
authors.forename: Harry B
authors.initials: HB
authors.lastname: Gray
mesh_terms: D001400:Azurin / Q000737:chemistry* / Q000378:metabolism; D003300:Copper / Q000737:chemistry; D004579:Electron Transport; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism
chemical_list: D009942:Organometallic Compounds; D001400:Azurin; C002744:3-nitrotyrosine; D014443:Tyrosine; D003300:Copper