Unexpected changes in photosystem I function in a cytochrome c6-deficient mutant of the cyanobacterium Synechocystis PCC 6803

• Published in: FEMS microbiology letters Vol. 213; no. 1; pp. 113 - 119
• Main Authors: Ardelean, I, Matthijs, H.C.P, Havaux, M, Joset, F, Jeanjean, R
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 16-07-2002; Blackwell
• Subjects: ammonium compounds; Bacteriology; Biological and medical sciences; carbon; copper; Copper - metabolism; Culture Media; Cyanobacteria - enzymology; Cyanobacteria - genetics; Cyanobacteria - growth & development; Cyanobacteria - metabolism; Cytochrome c6; Cytochromes - genetics; Cytochromes - metabolism; Cytochromes - physiology; Cytochromes f; electrons; energy; Flavodoxin; Fundamental and applied biological sciences. Psychology; Genetics; growth retardation; isiAB; light harvesting complex; Light-Harvesting Protein Complexes; Metabolism. Enzymes; Microbiology; mutants; Mutation; nitrogen; nutrient deficiencies; Operon; P700; petJ; Photosynthetic Reaction Center Complex Proteins - metabolism; Photosystem I; Photosystem I Protein Complex; plastocyanin; Quaternary Ammonium Compounds - pharmacology; Synechocystis sp. PCC 6803; Photosystem I; P700; Flavodoxin; Cytochrome c 6; isiAB; petJ; Cytochrome; Photosystem 1; Plastocyanin; Operon; Cyanobacteria; Electron transfer; Bacteria; Synechocystis; Copper; Cuproprotein; Chlorophyll a
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1016/S0378-1097(02)00801-7

Cytochrome
c
6, the product of the
petJ gene, is a photosynthetic electron carrier in cyanobacteria, which transfers electrons to photosystem I and which is synthesised under conditions of copper deficiency to functionally replace plastocyanin. The photosystem I photochemical activity (energy storage, photoinduced P700 redox changes) was examined in a
petJ-null mutant of
Synechocystis PCC 6803. Surprisingly, photosystem I activity in the
petJ-null mutant grown in the absence of copper was not much affected. However, in a medium with a low inorganic carbon concentration and with NH
4
+ ion as nitrogen source, the mutant displayed growth inhibition. Analysis showed that, especially in the latter, the
isiAB operon, encoding flavodoxin and CP43′, an additional chlorophyll
a antenna, was strongly expressed in the mutant. These proteins are involved in photosystem I function and organisation and are proposed to assist in prevention of overoxidation of photosystem I at its lumenal side and overreduction at its stromal side.