Site-directed mutagenesis of amino acid residues of D1 protein interacting with phosphatidylglycerol affects the function of plastoquinone QB in photosystem II.
Recent X-ray crystallographic analysis of photosystem (PS) II at 1.9-Å resolution identified 20 lipid molecules in the complex, five of which are phosphatidylglycerol (PG). In this study, we mutagenized amino acid residues S232 and N234 of D1, which interact with two of the PG molecules (PG664 and PG694), by site-directed mutagenesis in Synechocystis sp. PCC 6803 to investigate the role of the interaction in PSII. The serine and asparagine residues at positions 232 and 234 from the N-terminus were mutagenized to alanine and aspartic acid, respectively, and a mutant carrying both amino acid substitutions was also produced. Although the obtained mutants, S232A, N234D, and S232AN234D, exhibited normal growth, they showed decreased photosynthetic activities and slower electron transport from QA to QB than the control strain. Thermoluminescence analysis suggested that this slower electron transfer in the mutants was caused by more negative redox potential of QB, but not in those of QA and S2. In addition, the levels of extrinsic proteins, PsbV and PsbU, were decreased in PSII monomer purified from the S232AN234D mutant, while that of Psb28 was increased. In the S232AN234D mutant, the content of PG in PSII was slightly decreased, whereas that of monogalactosyldiacylglycerol was increased compared with the control strain. These results suggest that the interactions of S232 and N234 with PG664 and PG694 are important to maintain the function of QB and to stabilize the binding of extrinsic proteins to PSII.
Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
Kaichiro
K
Endo
Department of Frontier Bioscience, Hosei University, Koganei, Tokyo, 184-8584, Japan.|Research Center for Micro-Nano Technology, Hosei University, Koganei, Tokyo, 184-0003, Japan.
Naoki
N
Mizusawa
Photosynthesis Research Center, Graduate School of Natural Science and Technology, Okayama University, Tsushima-naka, Okayama, 700-8530, Japan.
Jian-Ren
JR
Shen
Faculty of Science, Tokyo University of Science, Kagurazaka, Shinjuku-ku, Tokyo, 162-8601, Japan.
Masato
M
Yamada
Faculty of Science, Tokyo University of Science, Kagurazaka, Shinjuku-ku, Tokyo, 162-8601, Japan.
Tatsuya
T
Tomo
Division of Materials Science, Faculty of Pure and Applied Science, University of Tsukuba, Ibaraki, 305-8573, Japan.
Hirohisa
H
Komatsu
Division of Materials Science, Faculty of Pure and Applied Science, University of Tsukuba, Ibaraki, 305-8573, Japan.
Masami
M
Kobayashi
Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo, 153-8902, Japan.
Koichi
K
Kobayashi
Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo, 153-8902, Japan. hwada@bio.c.u-tokyo.ac.jp.
Hajime
H
Wada
D019943:Amino Acid Substitution; D000596:Amino Acids / Q000378:metabolism; D004579:Electron Transport; D016297:Mutagenesis, Site-Directed; D010715:Phosphatidylglycerols / Q000378:metabolism*; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D010971:Plastoquinone / Q000378:metabolism*; D046939:Synechocystis / Q000378:metabolism*
D000596:Amino Acids; D010715:Phosphatidylglycerols; D045332:Photosystem II Protein Complex; D010971:Plastoquinone
D1; Phosphatidylglycerol; Photosystem II; Site-directed mutagenesis; Synechocystis sp. PCC 6803