Dataset Information

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).

SUBMITTER: Warren JJ

PROVIDER: S-EPMC3839300 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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Electron flow through nitrotyrosinate in Pseudomonas aeruginosa azurin.

Warren Jeffrey J JJ Herrera Nadia N Hill Michael G MG Winkler Jay R JR Gray Harry B HB

Journal of the American Chemical Society 20130716 30

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 ...[more]

PMID: 23859602

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Project description:The [Re(I)(CO)(3)(4,7-dimethyl-1,10-phenanthroline)(histidine-124)(tryptophan-122)] complex, denoted [Re(I)(dmp)(W122)], of Pseudomonas aeruginosa azurin behaves as a single photoactive unit that triggers very fast electron transfer (ET) from a distant (2 nm) Cu(I) center in the protein. Analysis of time-resolved (ps-?s) IR spectroscopic and kinetics data collected on [Re(I)(dmp)(W122)AzM] (in which M=Zn(II), Cu(II), Cu(I); Az=azurin) and position-122 tyrosine (Y), phenylalanine (F), and lysine (K) mutants, together with excited-state DFT/time-dependent (TD)DFT calculations and X-ray structural characterization, reveal the character, energetics, and dynamics of the relevant electronic states of the [Re(I)(dmp)(W122)] unit and a cascade of photoinduced ET and relaxation steps in the corresponding Re-azurins. Optical population of [Re(I)(imidazole-H124)(CO)(3)]?dmp (1)CT states (CT=charge transfer) is followed by around 110 fs intersystem crossing and about 600 ps structural relaxation to a (3)CT state. The IR spectrum indicates a mixed Re(I)(CO)(3),A?dmp/???(*)(dmp) character for aromatic amino acids A122 (A=W, Y, F) and Re(I)(CO)(3)?dmp metal-ligand charge transfer (MLCT) for [Re(I)(dmp)(K122)AzCu(II)]. In a few ns, the (3)CT state of [Re(I)(dmp)(W122)AzM] establishes an equilibrium with the [Re(I)(dmp(.-))(W122(.+))AzM] charge-separated state, (3)CS, whereas the (3)CT state of the other Y, F, and K122 proteins decays to the ground state. In addition to this main pathway, (3)CS is populated by fs- and ps-W(indole)?Re(II) ET from (1)CT and the initially "hot" (3)CT states, respectively. The (3)CS state undergoes a tens-of-ns dmp(.-)?W122(.+) ET recombination leading to the ground state or, in the case of the Cu(I) azurin, a competitively fast (?30 ns over 1.12?nm) Cu(I)?W(.+) ET, to give [Re(I)(dmp(.-))(W122)AzCu(II)]. The overall photoinduced Cu(I)?Re(dmp) ET through [Re(I)(dmp)(W122)AzCu(I)] occurs over a 2 nm distance in <50 ns after excitation, with the intervening fast (3)CT-(3)CS equilibrium being the principal accelerating factor. No reaction was observed for the three Y, F, and K122 analogues. Although the presence of [Re(dmp)(W122)AzCu(II)] oligomers in solution was documented by mass spectrometry and phosphorescence anisotropy, the kinetics data do not indicate any significant interference from the intermolecular ET steps. The ground-state dmp-indole ?-? interaction together with well-matched W/W(.+) and excited-state [Re(II)(CO)(3)(dmp(.-))]/[Re(I)(CO)(3)(dmp(.-))] potentials that result in very rapid electron interchange and (3)CT-(3)CS energetic proximity, are the main factors responsible for the unique ET behavior of [Re(I)(dmp)(W122)]-containing azurins.

Dataset Information

Electron flow through nitrotyrosinate in Pseudomonas aeruginosa azurin.

Publications

Electron flow through nitrotyrosinate in Pseudomonas aeruginosa azurin.

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