Aromatic structure of tyrosine-92 in the extrinsic PsbU protein of red algal photosystem II is important for its functioning |
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Authors: | Okumura Akinori Sano Masanori Suzuki Takehiro Tanaka Hiroyasu Nagao Ryo Nakazato Katsuyoshi Iwai Masako Adachi Hideyuki Shen Jian-Ren Enami Isao |
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Affiliation: | Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Tokyo 156-8850, Japan. |
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Abstract: | PsbU is one of the extrinsic proteins in red algal Photosystem II (PSII) and functions to optimize the availability of Ca(2+) and Cl(-) cofactors for water oxidation. To determine the functional residue of PsbU, we constructed various PsbU mutants from a red alga Cyanidium caldarium and reconstituted these mutants with the red algal PSII. The results revealed that Tyr-92 of PsbU, especially its aromatic ring, was essential for maintaining its function. From the crystal structure of PSII, Tyr-92 is located close to Pro-340 of D1, suggesting that the aromatic ring of Tyr-92 interacts with the CH group of Pro-340 of D1, and this CH/pi interaction is important for the optimal function of the Mn(4)Ca-cluster. |
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Keywords: | PsbU Extrinsic protein Oxygen evolution Photosystem II Red algae |
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