Overexpression of glutaredoxin-2 from cyanobacterium synechocystis PCC 6803 in Escherichia coli conferring enhanced salt stress tolerance

ABSTRACT

Glutaredoxin [Grx], widely found in bacteria, plants, and mammalian cells, is an electron carrier for ribonucleotide reductase and a general glutathione-disulfide reductase of importance for redox regulation. Cyanobacterium Synechocystis strain PCC 6803 contains two genes [slr1562 and ssr2061] encoding two glutaredoxins [Grx1 and Grx2, respectively]. The amino acid sequences deduced from both proteins share high identity with those of Grxs from other organisms. In the present study, we found that the steady-state transcript levels of ssr2061 were increased in the wild-type of Cyanobacterium cells under oxidative stress conditions imposed by high salinity [NaCl], chilling or application of H[2]O[2], methylviologen or t-butyl hydroperoxide. Moreover, the protein Grx2 encoded by ssr2061 was successfully overexpressed as a soluble fraction in Escherichia coli JM109. The transformed Escherichia coli cells showed high tolerance to NaCl [over than 700 mM] mediating growth inhibition compared to cells transformed with the vector alone]