D139N mutation of PsbP enhances the oxygen-evolving activity of photosystem II through stabilized binding of a chloride ion
| Autor: | Ko Imaizumi, Taishi Nishimura, Ryo Nagao, Keisuke Saito, Takeshi Nakano, Hiroshi Ishikita, Takumi Noguchi, Kentaro Ifuku |
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| Jazyk: | angličtina |
| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | PNAS Nexus. 1(3) |
| ISSN: | 2752-6542 |
| Popis: | Photosystem II (PSII) is a multi-subunit membrane protein complex that catalyzes light-driven oxidation of water to molecular oxygen. The chloride ion (Cl−) has long been known as an essential cofactor for oxygen evolution by PSII, and two Cl− ions (Cl-1 and Cl-2) have been found to specifically bind near the Mn4CaO5 cluster within the oxygen-evolving center (OEC). However, despite intensive studies on these Cl− ions, little is known about the function of Cl-2, the Cl− ion that is associated with the backbone nitrogens of D1-Asn338, D1-Phe339, and CP43-Glu354. In green plant PSII, the membrane extrinsic subunits—PsbP and PsbQ—are responsible for Cl− retention within the OEC. The Loop 4 region of PsbP, consisting of highly conserved residues Thr135–Gly142, is inserted close to Cl-2, but its importance has not been examined to date. Here, we investigated the importance of PsbP-Loop 4 using spinach PSII membranes reconstituted with spinach PsbP proteins harboring mutations in this region. Mutations in PsbP-Loop 4 had remarkable effects on the rate of oxygen evolution by PSII. Moreover, we found that a specific mutation, PsbP-D139N, significantly enhanced the oxygen-evolving activity in the absence of PsbQ, but not significantly in its presence. The D139N mutation increased the Cl− retention ability of PsbP and induced a unique structural change in the OEC, as indicated by light-induced Fourier transform infrared (FTIR) difference spectroscopy and theoretical calculations. Our findings provide insight into the functional significance of Cl-2 in the water-oxidizing reaction of PSII. 植物の光合成初期過程の酸素発生活性を向上させるアミノ酸変異を発見 --光合成・人工光合成の光エネルギー変換効率の向上へ期待--. 京都大学プレスリリース. 2022-08-18. |
| Databáze: | OpenAIRE |
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