Electron flow through nitrotyrosinate in Pseudomonas aeruginosa azurin

J Am Chem Soc. 2013 Jul 31;135(30):11151-8. doi: 10.1021/ja403734n. Epub 2013 Jul 16.

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).

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Azurin / chemistry*
  • Azurin / metabolism
  • Copper / chemistry
  • Electron Transport
  • Models, Molecular
  • Organometallic Compounds / chemistry
  • Protein Conformation
  • Pseudomonas aeruginosa*
  • Tyrosine / analogs & derivatives*
  • Tyrosine / chemistry
  • Tyrosine / metabolism

Substances

  • Organometallic Compounds
  • Azurin
  • 3-nitrotyrosine
  • Tyrosine
  • Copper