Proton-coupled electron transfer kinetics in tyrosine D of photosystem II

CHED 1434

Amaris Y. Evans, aevans@spelman.edu, Department of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, David L. Jenson, School of Chemistry and Biochemistry, Georgia Institute of Technology, Petit Institute for Bioengineering and Bioscience, Atlanta, GA 30332, and Bridgette A. Barry, School of Chemistry and Biochemistry and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332.
Photosystem II (PSII) is a trans-membrane protein complex that converts two molecules of water into four protons and molecular oxygen. The oxidation of water occurs in a metallocluster known as the oxygen evolving complex (OEC). Electron transfer through PSII is mediated in part by two luminal redox-active tyrosine residues. One of these residues, tyrosine D (YD), has been assigned as tyrosine 160 of the D2 polypeptide by site directed mutagenesis and isotopic labeling. Previous spectroscopic evidence has established that His 189 in the D2 subunit acts as a proton acceptor when tyrosine D is oxidized and then donates a proton to YDox when the radical is re-reduced. However, it is not known if this proton transfer is rate limiting for the electron transfer reaction. Utilizing EPR spectroscopy and 2H2O exchange we have examined the solvent isotope effect that occurs upon the reduction of the Tyrosine D radical. Supported by NIH GM43273.

 

Undergraduate Research Poster Session: Physical Chemistry
2:00 PM-4:00 PM, Monday, March 26, 2007 Hyatt Regency Chicago -- Riverside Center, Poster

Division of Chemical Education

The 233rd ACS National Meeting, Chicago, IL, March 25-29, 2007