Energetics and proton release in photosystem II from Thermosynechococcus elongatus with a D1 protein encoded by either the psbA2 or psbA3 gene |
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| Affiliation: | 1. I2BC, UMR CNRS 9198, CEA Saclay, 91191 Gif-sur-Yvette, France;2. Institut de Biologie Physico-Chimique, UMR CNRS 7141 and Sorbonne Université, 13 rue Pierre et Marie Curie, 75005 Paris, France;3. Proteo-Science Research Center, and Department of Chemistry, Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan;1. Institute of Biological Chemistry, Washington State University, Pullman, WA, USA;2. Department of Biochemistry and Center for Plant Biology, Purdue University, West Lafayette, IN 47907, USA;1. Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan;2. Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-Naka, Okayama 700-8530, Japan;3. Faculty of Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-Naka, Okayama 700-8530, Japan;4. Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan;1. A.N. Belozersky Institute of Physical-Chemical Biology, Moscow State University, 119992 Moscow, Leninskie Gory, 1, Building 40, Russia;2. . |
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| Abstract: | In the cyanobacterium Thermosynechococcus elongatus, there are three psbA genes coding for the Photosystem II (PSII) D1 subunit that interacts with most of the main cofactors involved in the electron transfers. Recently, the 3D crystal structures of both PsbA2-PSII and PsbA3-PSII have been solved [Nakajima et al., J. Biol. Chem. 298 (2022) 102668.]. It was proposed that the loss of one hydrogen bond of PheD1 due to the D1-Y147F exchange in PsbA2-PSII resulted in a more negative Em of PheD1 in PsbA2-PSII when compared to PsbA3-PSII. In addition, the loss of two water molecules in the Cl-1 channel was attributed to the D1-P173M substitution in PsbA2-PSII. This exchange, by narrowing the Cl-1 proton channel, could be at the origin of a slowing down of the proton release. Here, we have continued the characterization of PsbA2-PSII by measuring the thermoluminescence from the S2QA−/DCMU charge recombination and by measuring proton release kinetics using time-resolved absorption changes of the dye bromocresol purple. It was found that i) the Em of PheD1–/PheD1 was decreased by ∼30 mV in PsbA2-PSII when compared to PsbA3-PSII and ii) the kinetics of the proton release into the bulk was significantly slowed down in PsbA2-PSII in the S2TyrZ• to S3TyrZ and S3TyrZ• → (S3TyrZ•)’ transitions. This slowing down was partially reversed by the PsbA2/M173P mutation and induced by the PsbA3/P173M mutation thus confirming a role of the D1-173 residue in the egress of protons trough the Cl-1 channel. |
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