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pH‐Dependent Protonation of Surface Carboxylate Groups in PsbO Enables Local Buffering and Triggers Structural Changes
Author(s) -
Gerland Lisa,
Friedrich Daniel,
Hopf Linus,
Donovan Eavan J.,
Wallmann Arndt,
Erdmann Natalja,
Diehl Anne,
Bommer Martin,
Buzar Krzysztof,
Ibrahim Mohamed,
Schmieder Peter,
Dobbek Holger,
Zouni Athina,
Bondar AnaNicoleta,
Dau Holger,
Oschkinat Hartmut
Publication year - 2020
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.201900739
Subject(s) - carboxylate , protonation , chemistry , photosystem ii , thylakoid , proton , crystallography , catalysis , protein subunit , stereochemistry , photosynthesis , biophysics , photochemistry , biology , biochemistry , chloroplast , ion , organic chemistry , physics , quantum mechanics , gene
Photosystem II (PSII) catalyzes the splitting of water, releasing protons and dioxygen. Its highly conserved subunit PsbO extends from the oxygen‐evolving center (OEC) into the thylakoid lumen and stabilizes the catalytic Mn 4 CaO 5 cluster. The high degree of conservation of accessible negatively charged surface residues in PsbO suggests additional functions, as local pH buffer or by affecting the flow of protons. For this discussion, we provide an experimental basis, through the determination of p K a values of water‐accessible aspartate and glutamate side‐chain carboxylate groups by means of NMR. Their distribution is strikingly uneven, with high p K a values around 4.9 clustered on the luminal PsbO side and values below 3.5 on the side facing PSII. pH‐dependent changes in backbone chemical shifts in the area of the lumen‐exposed loops are observed, indicating conformational changes. In conclusion, we present a site‐specific analysis of carboxylate group proton affinities in PsbO, providing a basis for further understanding of proton transport in photosynthesis.