D1-Tyr246 and D2-Tyr244 in photosystem II: Insights into bicarbonate binding and electron transfer from Q to Q.

In photosystem II (PSII), D1-Tyr246 and D2-Tyr244 are symmetrically located at the binding site of the bicarbonate ligand of the non-heme Fe complex. Here, we investigated the role of the symmetrically arranged tyrosine pair, D1-Tyr246 and D2-Tyr244, in the function of PSII, by generating four chloroplast mutants of PSII from Chlamydomonas reinhardtii: D1-Y246F, D1-Y246T, D2-Y244F, and D2-Y244T. The mutants exhibited altered photoautotrophic growth, reduced PSII protein accumulation, and impaired O-evolving activity.