Two functional sites of phosphatidylglycerol for regulation of reaction of plastoquinone Q(B) in photosystem II.
Functional roles of an anionic lipid phosphatidylglycerol (PG) were studied in pgsA-gene-inactivated and cdsA-gene-inactivated/phycobilisome-less mutant cells of a cyanobacterium Synechocystis sp. PCC 6803, which can grow only in PG-supplemented media. 1) A few days of PG depletion suppressed oxygen evolution of mutant cells supported by p-benzoquinone (BQ). The suppression was recovered slowly in a week after PG re-addition. Measurements of fluorescence yield indicated the enhanced sensitivity of Q(B) to the inactivation by BQ. It is assumed that the loss of low-affinity PG (PG(L)) enhances the affinity for BQ that inactivates Q(B). 2) Oxygen evolution without BQ, supported by the endogenous electron acceptors, was slowly suppressed due to the direct inactivation of Q(B) during 10 days of PG depletion, and was recovered rapidly within 10h upon the PG re-addition. It is concluded that the loss of high-affinity PG (PG(H)) displaces Q(B) directly. 3) Electron microscopy images of PG-depleted cells showed the specific suppression of division of mutant cells, which had developed thylakoid membranes attaching phycobilisomes (PBS). 4) Although the PG-depletion for 14 days decreased the chlorophyll/PBS ratio to about 1/4, flourescence spectra/lifetimes were not modified indicating the flexible energy transfer from PBS to different numbers of PSII. Longer PG-depletion enhanced allophycocyanin fluorescence at 683nm with a long 1.2ns lifetime indicating the suppression of energy transfer from PBS to PSII. 5) Action sites of PG(H), PG(L) and other PG molecules on PSII structure are discussed.
Nagoya University, Graduate School of Science, Division of Material Science, Chikusa, Nagoya, Aichi, Japan. itoh@bio.phys.nagoya-u.ac.jp
Shigeru
S
Itoh
Takashi
T
Kozuki
Koji
K
Nishida
Yoshimasa
Y
Fukushima
Hisanori
H
Yamakawa
Ildikó
I
Domonkos
Hajnalka
H
Laczkó-Dobos
Mihály
M
Kis
Bettina
B
Ughy
Zoltán
Z
Gombos
D016227:Benzoquinones / Q000037:antagonists & inhibitors / Q000378:metabolism; D001665:Binding Sites / Q000187:drug effects; D002384:Catalysis / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D018360:Crystallography, X-Ray; D004579:Electron Transport / Q000187:drug effects; D008954:Models, Biological; D008958:Models, Molecular; D030781:Organisms, Genetically Modified; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology; D010715:Phosphatidylglycerols / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism*; D010860:Pigments, Biological / Q000737:chemistry / Q000378:metabolism; D010971:Plastoquinone / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D046939:Synechocystis / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
D016227:Benzoquinones; D010715:Phosphatidylglycerols; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological; C004532:quinone; D010971:Plastoquinone; D010100:Oxygen