Biological catalysis and energy transduction often rely on rapid charge transport over great distances (>20 E) within and between proteins. Many redox enzymes, especially those involved in the activation of strong chemical bonds (e.g. O-H, O=O, C-H), also require charge transport at high potentials. The combination of long-range and high potential charge transport places strict design requirements on enzyme scaffolds that carry out these reactions. Numerous redox enzymes use the redox active amino acids tryptophan (W) and tyrosine (Y) as redox 'way stations'to break long-range charge transport into shorter electron tunneling steps. This is known as 'hopping.'This research will examine the factors that influence hopping through Y in artificial blue-copper azurin model systems. All of these systems consist of a tyrosine residue situated between the azurin-CuI center and a (protein) surface attached photosensitizer. Our azurin models are specifically designed to account for the proton transfer that must accompany redox reactions of tyrosine. Introduction of an acidic tyrosine, 3-nitro-tyrosine (Aim 1), will allow for studies of hopping via tyrosinate, where proton transfer is not important. An important structural motif in biological Y-hopping systems is the positioning of a basic moiety near the phenolic proton of Y, which accepts the proton upon Y oxidation. A series of mutant azurins will be produced and studied where proton accepting groups, such as aspartate or histidine, are situated near Y (Aim 2). It is expected that the position of these bases will facilitate reversible electron transfer via tyrosine. By using the design criteria gleaned from Aims 1 and 2, azurin models where ultra-long-range charge transport (>30 E) occurs through Y will be explored (Aim 3).

Public Health Relevance

Reduction and oxidation (redox) pathways that involve the amino acid tyrosine are vital in a wide array of metabolic processes. Numerous diseases are associated with failure, disruption or malfunction of redox pathways. Elucidation of the fundamental factors that control biological redox chemistry of tyrosine will lead to deeper understanding of disease mechanisms and inform the development of new therapies.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
3F32GM095037-02S1
Application #
8537731
Study Section
Special Emphasis Panel (ZRG1-F04B-B (20))
Program Officer
Lees, Robert G
Project Start
2010-09-29
Project End
2013-08-31
Budget Start
2011-09-29
Budget End
2013-08-31
Support Year
2
Fiscal Year
2012
Total Cost
$48,495
Indirect Cost
Name
California Institute of Technology
Department
Chemistry
Type
Schools of Engineering
DUNS #
009584210
City
Pasadena
State
CA
Country
United States
Zip Code
91125
Gray, Harry B; Warren, Jeffery J; Winkler, Jay R et al. (2014) A Euclidean perspective on the unfolding of azurin: chain motion. J Biol Inorg Chem 19:555-63
Warren, Jeffrey J; Herrera, Nadia; Hill, Michael G et al. (2013) Electron flow through nitrotyrosinate in Pseudomonas aeruginosa azurin. J Am Chem Soc 135:11151-8
Whited, Charlotte A; Warren, Jeffrey J; Lavoie, Katherine D et al. (2013) Kinetics of CO Recombination to the Heme in Geobacillus Stearothermophilus Nitric Oxide Synthase. Polyhedron 58:134-138
Warren, Jeffrey J; Gray, Harry B; Winkler, Jay R et al. (2013) A Euclidean Perspective on the Unfolding of Azurin: Spatial Correlations. Mol Phys 111:922-929
Warren, Jeffrey J; Menzeleev, Artur R; Kretchmer, Joshua S et al. (2013) Long Range Proton-Coupled Electron Transfer Reactions of Bis(imidazole) Iron Tetraphenylporphyrins Linked to Benzoates. J Phys Chem Lett 4:519-523
Whited, Charlotte A; Warren, Jeffrey J; Lavoie, Katherine D et al. (2012) Gating NO release from nitric oxide synthase. J Am Chem Soc 134:27-30
Warren, Jeffrey J; Lancaster, Kyle M; Richards, John H et al. (2012) Inner- and outer-sphere metal coordination in blue copper proteins. J Inorg Biochem 115:119-26
Warren, Jeffrey J; Mayer, James M (2011) Proton-coupled electron transfer reactions at a heme-propionate in an iron-protoporphyrin-IX model compound. J Am Chem Soc 133:8544-51