Spectroscopic evidence for the symmetric location of tyrosines D and Z in photosystem II

Saturation-recovery EPR spectroscopic studies on photosystem II (PSII) membranes of spinach and on PSII core complexes of cyanobacterium Synechocystis sp. PCC 6803 reveal the symmetric location of tyrosines D and Z, relative to the non-heme Fe(II) in Mn-depleted photosystem II. The spin-lattice relaxation for both the YD and YZ radicals are increased by non-heme Fe(II). Spectral data confirm the presence of a C2 symmetry axis among the chromophores of PSII.