Zur ( FurB) is a key factor in the control of the oxidative stress response in A nabaena sp. PCC 7120.

Iron and zinc are necessary nutrients whose homeostasis is tightly controlled by members of the ferric uptake regulator ( FUR) superfamily in the cyanobacterium A nabaena sp. PCC7120. Although the link between iron metabolism and oxidative stress management is well documented, little is known about the connection between zinc homeostasis and the oxidative stress response in cyanobacteria. Zinc homeostasis in A nabaena is controlled by Zur, also named FurB. When overexpressed in E scherichia coli, Zur ( FurB) improved cell survival during oxidative stress. In order to investigate the possible correlation between Zur and the oxidative stress response in A nabaena, zur deletion and zur-overexpressing strains have been constructed, and the consequences of Zur imbalance evaluated. The lack of Zur increased sensitivity to hydrogen peroxide ( H2O2), whereas an excess of Zur enhanced oxidative stress resistance. Both mutants displayed pleiotropic phenotypes, including alterations on the filament surfaces observable by scanning electron microscopy, reduced content of endogenous H2O2 and altered expression of sodA, catalases and several peroxiredoxins. Transcriptional and biochemical analyses unveiled that the appropriate level of Zur is required for proper control of the oxidative stress response and allowed us to identify major antioxidant enzymes as novel members of the Zur regulon. [ABSTRACT FROM AUTHOR]