SALT TREATMENT INDUCES ACCUMULATION OF FLAVODOXIN IN THE CYANOBACTERIUM SYNECHOCYSTIS SP PCC-6803

Salt adaptation of Synechocystis sp. PCC 6803 leads to a changed protein composition of cells. A major salt-stress-induced protein was isolated in a preparative scale by nondenaturating gelelectrophoresis. Eighteen amino acid residues of the NH2-terminus were estimated by partial protein sequencing. This peptide resembles the NH2-terminal amino acid sequences of flavodoxins from several cyanobacterial strains. Beside sequence similarities, further biochemical and immunological properties indicate that flavodoxin is accumulated in high amounts in salt-adapted cells of Synechocystis. The synthesis of flavodoxin is also induced in iron-deficient and heat-shocked Synechocystis cells. A comparison of the protein composition of cells and kinetics of flavodoxin accumulation revealed that the induction of flavodoxin synthesis by salt and iron deficiency seems to be differently regulated.