Dataset Information

PH-Dependent Protonation of Surface Carboxylate Groups in PsbO Enables Local Buffering and Triggers Structural Changes.

ABSTRACT: 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 Mn4 CaO5 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 pKa values of water-accessible aspartate and glutamate side-chain carboxylate groups by means of NMR. Their distribution is strikingly uneven, with high pKa 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.

SUBMITTER: Gerland L

PROVIDER: S-EPMC7318136 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

pH-Dependent Protonation of Surface Carboxylate Groups in PsbO Enables Local Buffering and Triggers Structural Changes.

Gerland Lisa L Friedrich Daniel D Hopf Linus L Donovan Eavan J EJ Wallmann Arndt A Erdmann Natalja N Diehl Anne A Bommer Martin M Buzar Krzysztof K Ibrahim Mohamed M Schmieder Peter P Dobbek Holger H Zouni Athina A Bondar Ana-Nicoleta AN Dau Holger H Oschkinat Hartmut H

Chembiochem : a European journal of chemical biology 20200305 11

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<sub>4</sub> CaO<sub>5</sub> 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, throug ...[more]

PMID: 31930693

Similar Datasets

Project description:The electrochemical reduction of CO2 is widely studied as a sustainable alternative for the production of fuels and chemicals. The electrolyte's bulk pH and composition play an important role in the reaction activity and selectivity and can affect the extent of the buildup of pH gradients between the electrode surface and the bulk of the electrolyte. Quantifying the local pH and how it is affected by the solution species is desirable to gain a better understanding of the CO2 reduction reaction. Local pH measurements can be realized using Scanning Electrochemical Microscopy (SECM); however, finding a pH probe that is stable and selective under CO2 reduction reaction conditions is challenging. Here, we have used our recently developed voltammetric pH sensor to perform pH measurements in the diffusion layer during CO2 reduction using SECM, with high time resolution. Using a 4-hydroxylaminothiophenol (4-HATP)/4-nitrosothiophenol (4-NSTP) functionalized gold ultramicroelectrode, we compare the local pH developed above a gold substrate in an argon atmosphere, when only hydrogen evolution is taking place, to the pH developed in a CO2 atmosphere. The pH is monitored at a fixed distance from the surface, and the sample potential is varied in time. In argon, we observe a gradual increase of pH, while a plateau region is present in CO2 atmosphere due to the formation of HCO3 - buffering the reaction interface. By analyzing the diffusion layer dynamics once the sample reaction is turned "off", we gain insightful information on the time scale of the homogeneous reactions happening in solution and on the time required for the diffusion layer to fully recover to the initial bulk concentration of species. In order to account for the effect of the presence of the SECM tip on the measured pH, we performed finite element method simulations of the fluid and reaction dynamics. The results show the significant localized diffusion hindrance caused by the tip, so that in its absence, the pH values are more acidic than when the tip is present. Nonetheless, through the simulation, we can account for this effect and estimate the real local pH values across the diffusion layer.

Dataset Information

PH-Dependent Protonation of Surface Carboxylate Groups in PsbO Enables Local Buffering and Triggers Structural Changes.

Publications

pH-Dependent Protonation of Surface Carboxylate Groups in PsbO Enables Local Buffering and Triggers Structural Changes.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets