uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
Photochemical Tyrosine Oxidation in the Structurally Well-Defined alpha Y-3 Protein: Proton-Coupled Electron Transfer and a Long-Lived Tyrosine Radical
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
Show others and affiliations
2014 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, no 40, 14039-14051 p.Article in journal (Refereed) Published
Abstract [en]

Tyrosine oxidation-reduction involves proton-coupled electron transfer (PCET) and a reactive radical state. These properties are effectively controlled in enzymes that use tyrosine as a high-potential, one-electron redox cofactor. The alpha Y-3 model protein contains Y32, which can be reversibly oxidized and reduced in voltammetry measurements. Structural and kinetic properties of alpha Y-3 are presented. A solution NMR structural analysis reveals that Y32 is the most deeply buried residue in alpha Y-3. Time-resolved spectroscopy using a soluble flash-quench generated [Ru(2,2'-bipyridine)(3)](3+) oxidant provides high-quality Y32-O center dot absorption spectra. The rate constant of Y32 oxidation (k(pCET)) is pH dependent: 1.4 x 10(4) M-1 s(-1) (pH 5.5), 1.8 x 10(5) M-1 s(-1) (pH 8.5), 5.4 x 10(3) M-1 s(-1) (pD 5.5), and 4.0 x 10(4) M-1 s(-1) (pD 8.5). k(H)/k(D) of Y32 oxidation is 2.5 +/- 0.5 and 4.5 +/- 0.9 at pH(D) 5.5 and 8.5, respectively. These pH and isotope characteristics suggest a concerted or stepwise, proton-first Y32 oxidation mechanism. The photochemical yield of Y32-O center dot is 28-58% versus the concentration of [Ru(2,2'-bipyridine)(3)](3+). Y32-O center dot decays slowly, t(1/2) in the range of 2-10 s, at both pH 5.5 and 8.5, via radical-radical dimerization as shown by second-order kinetics and fluorescence data. The high stability of Y32-O center dot is discussed relative to the structural properties of the Y32 site. Finally, the static alpha Y-3 NMR structure cannot explain (i) how the phenolic proton released upon oxidation is removed or (ii) how two Y32-O center dot come together to form dityrosine. These observations suggest that the dynamic properties of the protein ensemble may play an essential role in controlling the PCET and radical decay characteristics of alpha Y-3.

Place, publisher, year, edition, pages
2014. Vol. 136, no 40, 14039-14051 p.
National Category
Chemical Sciences
URN: urn:nbn:se:uu:diva-236537DOI: 10.1021/ja503348dISI: 000343026700021PubMedID: 25121576OAI: oai:DiVA.org:uu-236537DiVA: diva2:766352
Swedish Research Council, 621-2012-3926, 623-2011-7189
Available from: 2014-11-26 Created: 2014-11-19 Last updated: 2014-11-26Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Glover, Starla D.Hammarström, Leif
By organisation
Physical Chemistry
In the same journal
Journal of the American Chemical Society
Chemical Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 500 hits
ReferencesLink to record
Permanent link

Direct link