Supercomplexes of IsiA and photosystem I in a mutant lacking subunit PsaL.
The cyanobacterium Synechocystis PCC 6803 grown under short-term iron-deficient conditions assembles a supercomplex consisting of a trimeric Photosystem I (PSI) complex encircled by a ring of 18 IsiA complexes. Furthermore, it has been shown that single or double rings of IsiA with up to 35 copies in total can surround monomeric PSI. Here we present an analysis by electron microscopy and image analysis of the various PSI-IsiA supercomplexes from a Synechocystis PCC 6803 mutant lacking the PsaL subunit after short- and long-term iron-deficient growth. In the absence of PsaL, the tendency to form complexes with IsiA is still strong, but the average number of complete rings is lower than in the wild type. The majority of IsiA copies binds into partial double rings at the side of PsaF/J subunits rather than in complete single or double rings, which also cover the PsaL side of the PSI monomer. This indicates that PsaL facilitates the formation of IsiA rings around PSI monomers but is not an obligatory structural component in the formation of PSI-IsiA complexes.
Kouril
Roman
R
Department of Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Yeremenko
Nataliya
N
D'Haene
Sandrine
S
Oostergetel
Gert T
GT
Matthijs
Hans C P
HC
Dekker
Jan P
JP
Boekema
Egbert J
EJ
D001426:Bacterial Proteins / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D008854:Microscopy, Electron; D009154:Mutation; D045331:Photosystem I Protein Complex / Q000235:genetics* / Q000378:metabolism*; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; C082500:photosystem I, psaL subunit; C076726:chlorophyll A binding protein CP43, Cyanobacteria