The D1-V185N mutation alters substrate water exchange by stabilizing alternative structures of the Mn4Ca-cluster in photosystem II

Casper de Lichtenberg; Anton P Avramov; Minquan Zhang; Fikret Mamedov; Robert L Burnap; Johannes Messinger

doi:10.1016/j.bbabio.2020.148319

The D1-V185N mutation alters substrate water exchange by stabilizing alternative structures of the Mn₄Ca-cluster in photosystem II

Biochim Biophys Acta Bioenerg. 2021 Jan 1;1862(1):148319. doi: 10.1016/j.bbabio.2020.148319. Epub 2020 Sep 23.

Authors

Casper de Lichtenberg¹, Anton P Avramov², Minquan Zhang², Fikret Mamedov³, Robert L Burnap², Johannes Messinger⁴

Affiliations

¹ Department of Chemistry, Umeå University, Linnaeus väg 6 (KBC huset), SE-901 87 Umeå, Sweden; Molecular Biomimetics, Department of Chemistry - Ångström, Uppsala University, POB 523, SE-75120 Uppsala, Sweden.
² Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078, United States.
³ Molecular Biomimetics, Department of Chemistry - Ångström, Uppsala University, POB 523, SE-75120 Uppsala, Sweden.
⁴ Department of Chemistry, Umeå University, Linnaeus väg 6 (KBC huset), SE-901 87 Umeå, Sweden; Molecular Biomimetics, Department of Chemistry - Ångström, Uppsala University, POB 523, SE-75120 Uppsala, Sweden. Electronic address: johannes.messinger@kemi.uu.se.

PMID: 32979346
DOI: 10.1016/j.bbabio.2020.148319

Abstract

In photosynthesis, the oxygen-evolving complex (OEC) of the pigment-protein complex photosystem II (PSII) orchestrates the oxidation of water. Introduction of the V185N mutation into the D1 protein was previously reported to drastically slow O₂-release and strongly perturb the water network surrounding the Mn₄Ca cluster. Employing time-resolved membrane inlet mass spectrometry, we measured here the H₂¹⁸O/H₂¹⁶O-exchange kinetics of the fast (W_f) and slow (W_s) exchanging substrate waters bound in the S₁, S₂ and S₃ states to the Mn₄Ca cluster of PSII core complexes isolated from wild type and D1-V185N strains of Synechocystis sp. PCC 6803. We found that the rate of exchange for W_s was increased in the S₁ and S₂ states, while both W_f and W_s exchange rates were decreased in the S₃ state. Additionally, we used EPR spectroscopy to characterize the Mn₄Ca cluster and its interaction with the redox active D1-Tyr161 (Y_Z). In the S₂ state, we observed a greatly diminished multiline signal in the V185N-PSII that could be recovered by addition of ammonia. The split signal in the S₁ state was not affected, while the split signal in the S₃ state was absent in the D1-V185N mutant. These findings are rationalized by the proposal that the N185 residue stabilizes the binding of an additional water-derived ligand at the Mn1 site of the Mn₄Ca cluster via hydrogen bonding. Implications for the sites of substrate water binding are discussed.

Keywords: EPR; Manganese cluster; O-O bond formation; Photosystem II; Substrate water exchange; Water oxidation.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Amino Acid Substitution
Bacterial Proteins / genetics
Bacterial Proteins / metabolism*
Mutation, Missense*
Photosystem II Protein Complex / genetics
Photosystem II Protein Complex / metabolism*
Synechocystis / genetics
Synechocystis / metabolism*
Water / metabolism*

Substances

Bacterial Proteins
Photosystem II Protein Complex
Water