Proteomic alterations of Escherichia coli by paraquat
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Date
2010-11-17
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Abstract
Paraquat (PQ; a widely used herbicide) exerts its harmful effect to human, mammals and microorganisms upon intracellular conversion to superoxide radical. Cellular responses against toxic paraquat remain not fully understood, especially on the adaptive metabolic changes as a consequence of oxidative burden. In this study, alterations of metabolic processes of Escherichia
coli (E. coli) by paraquat were systematically investigated by two-dimensional gel electrophoresis (2-DE) in conjunction with peptide mass fingerprinting (PMF). In host cells, the first line mechanism was scrutinized by a remarkable induction of endogenous superoxide
dismutase (E. coli SOD). The second line involved in the metabolic adaptation and compensation for energy production by up- or down-regulation of the enzymes implicated in glycolysis and tricarboxylic acid cycle. Notably, down-regulation of aconitase enzyme and changes of enzyme isoform from the acidic (pI~5.29) to the higher basidic form (pI~5.59) were detected. Meanwhile, up-regulation of fumarase approximately 4-5 folds were observed. Importantly,
overexpression of human manganese superoxide dismutase (human Mn-SOD) in E. coli cells
could in turn down-regulate the expression of fumarase enzyme. This observation was not
found when the cells expressing human catalase were tested. Other mechanisms such as changes of purine nucleoside phosphorylase and protein transporters (D-ribose-binding protein and oligopeptide binding protein) were also accounted. However, among all the differentially
expressed proteins, the fumarase enzyme is evidenced to be a major target responsible
for superoxide-generating paraquat, which may further be applied as a potential biomarker for paraquat toxicity in the future.
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Keywords
Escherichia coli, oxidative stress, proteomic, superoxide dismutase, two-dimensional gel electrophoresis