D1-Asp170 Is Structurally Coupled to the Oxygen Evolving Complex in Photosystem II As Revealed by Light-Induced Fourier Transform Infrared Difference Spectroscopy†

We report both mid-frequency (1800−1200 cm-1) and low-frequency (670−350 cm-1) S2/S1 FTIR difference spectra of photosystem II (PSII) particles isolated from wild-type* and D1-D170H mutant cells of the cyanobacterium Synechocystis sp. PCC 6803. Both mid- and low-frequency S2/S1 spectra of the Synechocystis wild-type* PSII particles closely resemble those from spinach PSII samples, which confirms an earlier result by Noguchi and co-workers [Noguchi, T., Inoue, Y., and Tang, X.-S. (1997) Biochemistry 36, 14705−14711] and indicates that the coordination environment of the oxygen evolving complex (OEC) in Synechocystis is very similar to that in spinach. We also found that there is no appreciable difference between the mid-frequency S2/S1 spectra of wild-type* and of D1-D170H mutant PSII particles, from which we conclude that D1-Asp170 does not undergo a significant structural change during the S1 to S2 transition. This result also suggests that, if D1-Asp170 ligates Mn, it does not ligate the Mn ion that is ...