MUTATIONAL ANALYSIS OF THE GENES ENCODING THE PHOTOSYSTEM-II PROTEINSIN CYANOBACTERIUM SYNECHOCYSTIS SP 6803

Chlorophyll-binding protein CP43 and cytochrome b559, encoded by psbC and psbF/F genes, are the components of photosystem II (PS II). Three psbC- and four psbE/F- mutants were isolated from the collection of PS II-deficient mutants of the cyanobacterium Synechocystis sp. 6803. Re storation of photosynthetic activity was achieved by transformation of psbE/F- mutants with cloned psbE/F gene cluster from wild type cells and each of psbC- mutants - with specific part of wild type psbC gene. DNA fragments carrying the mutations were isolated from mutant cells and sequenced. The mutations which affect PS II activity were identifi ed in psbC gene as <<frameshift>> mutation, stop-codon formation, or a s deletion of three nucleotides resulting in loss of one of three Phe residues in position 422-424 of CP43. Sequence of mutant psbE/F genes revealed single mutations resulting in deletion of Phe-36 or substitut ion of Pro-63 for Leu in alpha-subunit and Val-29 for Phe in beta-subu nit of cytochrome b559.