Structural changes in the acceptor site of photosystem ii upon Ca2+/Sr2+ exchange in the MN4CAO5 cluster site and the possible long‐range interactions

Abstract

The Mn4CaO5 cluster site in the oxygen‐evolving complex (OEC) of photosystem II (PSII) undergoes structural perturbations, such as those induced by Ca2+/Sr2+ exchanges or Ca/Mn removal. These changes have been known to induce long‐range positive shifts (between +30 and +150 mV) in the redox potential of the primary quinone electron acceptor plastoquinone A (QA), which is located 40 Å from the OEC. To further investigate these effects, we reanalyzed the crystal structure of Sr‐PSII resolved at 2.1 Å and compared it with the native Ca‐PSII resolved at 1.9 Å. Here, we focus on the acceptor site and report the possible long‐range interactions between the donor, Mn4Ca(Sr)O5 cluster, and acceptor sites.