Abstract
Superoxide dismutase (SOD)-deficient Escherichia coli OX326Acells are protected against chemically-induced oxidative stress by expression of the chaperonin GroESL. This protection is equivalent to expression of superoxide dismutase even though GroESL has no inherent SOD activity. Co-overexpression of GroESL and SOD in the same cells results in higher protein yields of SOD and greater metallation of SOD when compared with expression of SOD alone. Greater metallation results in the higher specific activity of SOD that is observed in heat shock, and is not due to increased synthesis of SOD mRNA or protein.
Highlights
Escherichia coli has two cytoplasmic superoxide dismutases (EC 1.15.1.1, Superoxide dismutase (SOD)): an iron-containing SOD (FeSOD) encoded by the sodB gene [1,2,3] and a manganese-containing SOD (MnSOD) encoded by the sodA gene [4]
In order to observe any in vivo effect, the chaperone GroEL and its cofactor GroES may have on the solubility and specific activity of FeSOD and MnSOD, kanamycinresistant OX326A cells (ΔsodA ΔsodB) were co-transformed with pTET-GroESL and pTH-FeSOD or pTHMnSOD respectively. pTH-1 is a derivative of pTrc99A which is an expression vector incorporating a tac promoter
There is evidence that aerobic heat shock produces conditions of oxidative stress [23] and we have investigated whether SODs are influenced by heat shock
Summary
Escherichia coli has two cytoplasmic superoxide dismutases (EC 1.15.1.1, SOD): an iron-containing SOD (FeSOD) encoded by the sodB gene [1,2,3] and a manganese-containing SOD (MnSOD) encoded by the sodA gene [4] These two antioxidant enzymes have similar catalytic activity and protect the cell by removing supe-. Hunter / Health 5 (2013) 1719-1729 shock at 48 ̊C increased the SOD activity by a factor of two These authors identified MnSOD as the responsible agent. During heat shock, the observed increase in MnSOD activity in E. coli is demonstrated to be a post-translational phenomenon and is not due to increased transcription or protein synthesis
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