Modification of the pheophytin redox potential in Thermosynechococcus elongatus Photosystem II with PsbA3 as D1.
In Photosystem II (PSII) of the cyanobacterium Thermosynechococcus elongatus, glutamate 130 in the high-light variant of the D1-subunit (PsbA3) was changed to glutamine in a strain lacking the two other genes for D1, psbA1 and psbA2. The resulting PSII (PsbA3/Glu130Gln) was compared with those from the "native" high-light (PsbA3-PSII) and low-light (PsbA1-PSII) variants, which differ by 21 amino acid including Glu130Gln. H-bonding from D1-Glu130Gln to the primary electron acceptor, PheophytinD1 (PheoD1), is known to affect the Em of the PheoD1/PheoD1(-) couple. The Gln130 mutation here had little effect on water splitting, charge accumulation and photosensitivity but did slow down S2QA(-) charge recombination and up-shift the thermoluminescence while increasing its yield. These changes were consistent with a ≈-30mV shift of the PheoD1/PheoD1(-)Em, similar to earlier single site-mutation results from other species and double the ≈-17mV shift seen for PsbA1-PSII versus PsbA3-PSII. This is attributed to the influence of the other 20 amino-acids that differ in PsbA3. A computational model for simulating S2QA(-) recombination matched the experimental trend: the S2QA(-) recombination rate in PsbA1-PSII differed only slightly from that in PsbA3-PSII, while in Glu130-PsbA3-PSII there was a more pronounced slowdown of the radical pair decay. The simulation predicted a major effect of the PheoD1/PheoD1(-) potential on (1)O2 yield (~60% in PsbA1-PSII, ~20% in PsbA3-PSII and ~7% in Gln130-PsbA3-PSII), reflecting differential sensitivities to high light.
Proteo-Science Research Center, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan; PRESTO, Science and Technology Agency (JST), 4-1-8, Honcho, Kawaguchi, Saitama 332-0012, Japan. Electronic address: miwa.sugiura@ehime-u.ac.jp.
Miwa
M
Sugiura
Chizuko
C
Azami
Kazumi
K
Koyama
A William
AW
Rutherford
Fabrice
F
Rappaport
Alain
A
Boussac
D000458:Cyanobacteria / Q000737:chemistry* / Q000378:metabolism; D004579:Electron Transport; D018698:Glutamic Acid / Q000235:genetics; D005973:Glutamine / Q000235:genetics; D008027:Light; D009154:Mutation; D010084:Oxidation-Reduction; D010674:Pheophytins / Q000737:chemistry* / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D010674:Pheophytins; D045332:Photosystem II Protein Complex; C422369:photosystem II, psbA subunit; D005973:Glutamine; D018698:Glutamic Acid
2-(N-morpholino)ethanesulfonic acid; 3-(3,4-dichlorophenyl)-1,1-dimethylurea; 43H; Chl; Chl monomer of P(680) on the D1 or D2 side, respectively; Cyanobacterium; DCMU; E(m); MES; P(680); P(D1) and P(D2); PPBQ; PQ; PSII; Pheo(D1); Pheophytin; Photosystem II; PsbA; Q(A); Q(B); Singlet oxygen; T. elongatus strain with a His-tag on the C terminus of CP43; TL; Thermoluminescence; Thermosynechococcus elongatus; WT*1, WT*2, WT*3; cells containing only the psbA(1), psbA(2), psbA(3) gene, respectively; chlorophyll; chlorophyll dimer acting as the second electron donor; n-dodecyl-β-maltoside; phenyl p-benzoquinone; pheophytin; plastoquinone 9; primary quinone acceptor; redox potential versus SHE; secondary quinone acceptor; β-DM