245 GHz high-field EPR study of tyrosine-D zero and tyrosine-Z zero in mutants of photosystem II.
A 245 GHz 8.7 T high-field EPR study of tyrosine-D (TyrD zero) and tyrosine-Z (TyrZ zero) radicals of photosystem II (PSII) from Synechocystis PCC 6803 was carried out. Identical principal g values for the wild-type Synechocystis and spinach TyrD zero showed that the two radicals were in similar electrostatic environments. By contrast, the principal g values of the TyrD zero in the D2-His189Gln mutant of Synechocystis were different from those of the wild-type and spinach radicals and were similar to those of the tyrosyl radical in ribonucleotide reductase. These comparisons indicate that the D2-His189Gln mutant TyrD zero is not hydrogen-bonded or is only weakly so. The HF-EPR spectrum of TyrZ zero was obtained from the D2-Tyr160Phe mutant that lacks TyrD zero. The principal g values were nearly identical to those of the wild-type TyrD zero. The low-field edge of the TyrZ zero spectrum was much broader than at the other two principal g values and was also much broader than the TyrD zero spectrum. From the identical g values and previous work on tyrosyl radical g values [Un S., Atta M., Fontecave, M., & Rutherford, A. W. (1995) J. Am. Chem. Soc. 117, 10713-10719], it was concluded that TyrZ zero, like TyrD zero, is hydrogen-bonded The broadness of the gx component was interpreted as a distribution in strength of the hydrogen-bonding due to disorder in the protein environment about TyrZ zero.
URA1290 CNRS, Department Biologie Cellulaire et Moléculaire, CEA-Saclay, Gif-sur-Yvette, France.
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D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006860:Hydrogen Bonding; D009154:Mutation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D045332:Photosystem II Protein Complex; D017550:Spectroscopy, Fourier Transform Infrared; D014443:Tyrosine / Q000737:chemistry*
D005609:Free Radicals; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D014443:Tyrosine