Phosphatidylglycerol is essential for oligomerization of photosystem I reaction center.
Our earlier studies with the pgsA mutant of Synechocystis PCC6803 demonstrated the important role of phosphatidylglycerol (PG) in PSII dimer formation and in electron transport between the primary and secondary electron-accepting plastoquinones of PSII. Using a long-term depletion of PG from pgsA mutant cells, we could induce a decrease not only in PSII but also in PSI activity. Simultaneously with the decrease in PSI activity, dramatic structural changes of the PSI complex were detected. A 21-d PG depletion resulted in the degradation of PSI trimers and concomitant accumulation of monomer PSI. The analyses of PSI particles isolated by MonoQ chromatography showed that, following the 21-d depletion, PSI trimers were no longer detectable in the thylakoid membranes. Immunoblot analyses revealed that the PSI monomers accumulating in the PG-depleted mutant cells do not contain PsaL, the protein subunit thought to be responsible for the trimer formation. Nevertheless, the trimeric structure of PSI reaction center could be restored by readdition of PG, even in the presence of the protein synthesis inhibitor lincomycin, indicating that free PsaL was present in thylakoid membranes following the 21-d PG depletion. Our data suggest an indispensable role for PG in the PsaL-mediated assembly of the PSI reaction center.
Domonkos
Ildikó
I
Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, H-6701 Szeged, Hungary. domonkos@nucleus.szbk.u-szedeg.hu
Malec
Przemyslaw
P
Sallai
Anna
A
Kovács
László
L
Itoh
Kunihiro
K
Shen
Gaozhong
G
Ughy
Bettina
B
Bogos
Balázs
B
Sakurai
Isamu
I
Kis
Mihály
M
Strzalka
Kazimierz
K
Wada
Hajime
H
Itoh
Shigeru
S
Farkas
Tibor
T
Gombos
Zoltán
Z
D002734:Chlorophyll / Q000378:metabolism; D000458:Cyanobacteria / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D019281:Dimerization; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D009154:Mutation; D010715:Phosphatidylglycerols / Q000378:metabolism* / Q000494:pharmacology; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D020524:Thylakoids / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
D008055:Lipids; D010715:Phosphatidylglycerols; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll