Superoxide Dismutases of Escherichia coli : Intracellular Localization and Functions

Abstract

Escherichia coli B contains two superoxide dismutases which differ with respect to their localization within the cell, the nature of their prosthetic metals, their responses to changes in p02, and their functions. One of these enzymes, which was liberated from the cells by osmotic shock and which was therefore presumed to be localized in the periplasmic space, is an iron-containing superoxide dismutase. The amount of this iron enzyme did not vary in response to changes in p°2 during growth. In contrast, the other superoxide dismutase was not solubilized by osmotic shock, was a mangano-protein, and was found in greater amounts in cells which had been grown at high pO,. E. coli, which had low levels of the iron-enzyme and high levels of the mangano-enzyme, as a consequence of growth in iron-deficient aerated medium, was killed by exposure to an exogenous flux of 02-which was generated either photochemically or enzymatically. The addition of bovine superoxide dismutase to the suspending medium protected these cells against this stress. On the other hand, E. coli, which had high levels of the iron-enzyme and low levels of the mangano-enzyme, as a consequence of growth in iron-rich anaerobic medium, was resistant to exogeneous 02.-On the basis of these and of previously reported results (4a, Yost, F. J. and I. Fridovich, J. Biol. Chem., 1973, in press), it appears that the iron superoxide dismutase, of the periplasmic space, serves as a defense against exogenous°2-, whereas the mangano-superoxide dismutase, in the matrix of these cells, serves to counter the toxicity of endogenous 02.

Superoxide Dismutase, Catalase and Glutathione Peroxidase: Solutions to the Problems of Living With Oxygen

“…Cells of Escherichia coli grown under 100% O2 were much more resistant to hyperbaric O2 than cells grown under air, but this was not true for Bacillus subtilis (Gregory and Fridovich, 1973b). Cells of Escherichia coli B depleted of periplasmic superoxide dismutase by growth on an iron-deficient medium were much more rapidly killed by 02" than normal cells (Gregory et al, 1973). Mutants of E. coli temperature-sensitive in superoxide dismutase activity show a comparable defect in their ability to grow in O2 (Gregory and Fridovich, 1974).…”

“…E.xposure of membranes to a source of O2~ causes peroxidation. Bacteria and viruses exposed to 02~ are rapidly killed (Lavalle, Michelson and Dimitrijevic, 1973;Gregory, Yost and Fridovich, 1973;Gregory and Fridovich, 1974). Production of Oj" may be responsible for the effects of bipyridyl herbicides (Farrington et aL, 1973) and for the nerve degeneration caused by injecting animals with 6-hydroxy-dopamine (Heikkila and Cohen, 1973).…”

“…The presence of superoxide dismutase activity in aerobes but not in anaerobes suggests a role in protection against oxygen free-radicals. In experiments in vitro, superoxide dismutase has been shown to protect subcellular organelles and bacteria against oxidative damage (Pederson andAust, 1972, 1973;Fee and Teitelbaum, 1972;Zimmermann et al, 1973;Lavalle et al, 1973;Gregory et al, 1973). Recent experiments suggest that superoxide dismutase may be able to catalyse the removal of singlet oxygen as well as of O^" (Paschen and Weser, 1973).…”

Macrophage microbicidal activity. Correlation between phagocytosis-associated oxidative metabolism and the killing of candida by macrophages

“…Mandell has reported that neutmphils killed a low-catalase strain of S. aureus better than a high-catalase strain (23). On the other hand, Gregory et al found that induction of increased concentrations of SOD in Escherichia coli by growth in oxygenated medium protected bacteria against endogenous 02-resulting from further increases in pO2, but offered no protection against exogenous 02-generated by photochemical or xanthine oxidase systems (24). In experiments reported here, neither species of candida scavenged H202 or 02-derived from chemical sources or macrophages, and C. albicans was killed at least as easily as C. parapsilosis by exogenously generated oxygen radicals.…”

The superoxide dismutase SodA is targeted to the periplasm in a SecA‐dependent manner by a novel mechanism

“…Proteins consisting of the N-terminal 59 amino acids of E. coli SodA or SodB fused to PhoA were both exported to the periplasm, although both proteins are considered cytoplasmic in E. coli (Britton and Fridovich, 1977;Serres et al, 2004). Interestingly, E. coli SodB was originally described as a periplasmic protein (Gregory et al, 1973) and export of an E. coli SodB-PhoA fusion protein was also previously reported by Bailey and Manoil (2002). Possibly this is an indication that while E. coli SodA and SodB are targeting-competent, these proteins are only exported under certain conditions, and remain within the cytoplasm under standard laboratory conditions.…”