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Title: Spin-density distribution, conformation, and hydrogen bonding of the redox-active tyrosine Y{sub z} in photosystem II from multiple electron magnetic-resonance spectroscopies: Implications for photosynthetic oxygen evolution

Abstract

The oxidized form of the redox-active Y{sub Z} tyrosyl residue involved in photosynthetic oxygen evolution has been generated and trapped in Mn-depleted Photosystem II core complexes from a D2-Y160F mutant strain of Synechocystis 6803. This system eliminates interference from P{sub 700}{sup +} and Y{sub D}D+{center_dot} and allowed characterization of Y{sub Z}{sup {center_dot}} by using a combination of specific {sup 2}H-labeling and electron magnetic-resonance techniques that included CW-EPR, frequency-modulated and transient detected ENDOR, and {sup 2}H-ESEEM. Using these complementary techniques, we have carried out a detailed evaluation of the hyperfine structure of Y{sub Z}{sup {center_dot}} and obtained the dipolar interactions to weakly coupled nuclei, the strongly anisotropic tensors of the ring-hydrogens, and the more isotropic interactions to the {Beta}-methylene site. We conclude that tyrosyl radicals are not tuned to specific function by large-scale modulations of their spin density through hydrogen-bonding effects. We suggest a hydrogen-atom transfer function for Y{sub Z} in water oxidation. Within this model, the (Mn){sub 4}/Y{sub Z} center forms the Oxygen-Evolving Complex of Photosystem II where the (Mn){sub 4} cluster binds substrate water and delocalizes oxidizing equivalents and Y{sub Z} acts by abstracting hydrogens from substrate water in either a concerted or sequential fashion. 71 refs., 8 figs.,more » 2 tabs.« less

Authors:
 [1]; ;  [2]; ; ; ;  [3];  [1]
  1. Stockholm Univ. (Sweden)
  2. E. I. Du Pont deNemours and Co., Wilmington, DE (United States)
  3. Michigan State Univ., East Lansing, MI (United States)
Publication Date:
OSTI Identifier:
136297
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 117; Journal Issue: 41; Other Information: PBD: 18 Oct 1995
Country of Publication:
United States
Language:
English
Subject:
55 BIOLOGY AND MEDICINE, BASIC STUDIES; 40 CHEMISTRY; 66 PHYSICS; OXYGEN; PHOTOSYNTHESIS; TYROSINE; REDOX REACTIONS; ENERGY SPECTRA; COMPLEXES; HYDROGEN; PHOTOSYNTHETIC REACTION CENTERS; CHEMICAL BONDS; OXIDATION; ENDOR; ELECTRON SPIN RESONANCE; ELECTRONIC STRUCTURE

Citation Formats

Tommos, C, Michigan State Univ., East Lansing, MI, Tang, X S, Diner, B A, Warncke, K, Hoganson, C W, McCracken, J, Babcock, G T, and Styring, S. Spin-density distribution, conformation, and hydrogen bonding of the redox-active tyrosine Y{sub z} in photosystem II from multiple electron magnetic-resonance spectroscopies: Implications for photosynthetic oxygen evolution. United States: N. p., 1995. Web. doi:10.1021/ja00146a017.
Tommos, C, Michigan State Univ., East Lansing, MI, Tang, X S, Diner, B A, Warncke, K, Hoganson, C W, McCracken, J, Babcock, G T, & Styring, S. Spin-density distribution, conformation, and hydrogen bonding of the redox-active tyrosine Y{sub z} in photosystem II from multiple electron magnetic-resonance spectroscopies: Implications for photosynthetic oxygen evolution. United States. https://doi.org/10.1021/ja00146a017
Tommos, C, Michigan State Univ., East Lansing, MI, Tang, X S, Diner, B A, Warncke, K, Hoganson, C W, McCracken, J, Babcock, G T, and Styring, S. Wed . "Spin-density distribution, conformation, and hydrogen bonding of the redox-active tyrosine Y{sub z} in photosystem II from multiple electron magnetic-resonance spectroscopies: Implications for photosynthetic oxygen evolution". United States. https://doi.org/10.1021/ja00146a017.
@article{osti_136297,
title = {Spin-density distribution, conformation, and hydrogen bonding of the redox-active tyrosine Y{sub z} in photosystem II from multiple electron magnetic-resonance spectroscopies: Implications for photosynthetic oxygen evolution},
author = {Tommos, C and Michigan State Univ., East Lansing, MI and Tang, X S and Diner, B A and Warncke, K and Hoganson, C W and McCracken, J and Babcock, G T and Styring, S},
abstractNote = {The oxidized form of the redox-active Y{sub Z} tyrosyl residue involved in photosynthetic oxygen evolution has been generated and trapped in Mn-depleted Photosystem II core complexes from a D2-Y160F mutant strain of Synechocystis 6803. This system eliminates interference from P{sub 700}{sup +} and Y{sub D}D+{center_dot} and allowed characterization of Y{sub Z}{sup {center_dot}} by using a combination of specific {sup 2}H-labeling and electron magnetic-resonance techniques that included CW-EPR, frequency-modulated and transient detected ENDOR, and {sup 2}H-ESEEM. Using these complementary techniques, we have carried out a detailed evaluation of the hyperfine structure of Y{sub Z}{sup {center_dot}} and obtained the dipolar interactions to weakly coupled nuclei, the strongly anisotropic tensors of the ring-hydrogens, and the more isotropic interactions to the {Beta}-methylene site. We conclude that tyrosyl radicals are not tuned to specific function by large-scale modulations of their spin density through hydrogen-bonding effects. We suggest a hydrogen-atom transfer function for Y{sub Z} in water oxidation. Within this model, the (Mn){sub 4}/Y{sub Z} center forms the Oxygen-Evolving Complex of Photosystem II where the (Mn){sub 4} cluster binds substrate water and delocalizes oxidizing equivalents and Y{sub Z} acts by abstracting hydrogens from substrate water in either a concerted or sequential fashion. 71 refs., 8 figs., 2 tabs.},
doi = {10.1021/ja00146a017},
url = {https://www.osti.gov/biblio/136297}, journal = {Journal of the American Chemical Society},
number = 41,
volume = 117,
place = {United States},
year = {1995},
month = {10}
}