Proteomic Profiling of Escherichia Coli in Response to Heavy Metals Stress

Over utilization of natural resources and growing trend of industrialization raise a global concern on environmental toxic metals to living organisms. Using two-dimensional gel electrophoresis (2-DE) in combination with peptide mass fingerprinting, significant changes of differentially expressed proteins in response to toxic doses of cadmium (0.2 mM), zinc (0.6 mM), copper (1.2 mM) and mercuric ions (0.05 mM) were detected and implied multi-involvement of cellular processes. Cadmium ions exerted the toxicity by down-regulation of enzymes involved in the energy metabolism such as aconitase, malic enzyme and enolase. These suppressing effects also took place for components involved in the active transport (dipeptide binding protein and oligopeptide transport periplasmic binding protein) and protein synthesis machinery (elongation factor-Tu and 30S ribosomal protein S1). More importantly, the presence of Cd rendered a markedly increase (> 5 folds) of 3,4-dihydroxy-2-butanone 4-phosphate (DHBP) synthase, an enzyme implicated in riboflavin biosynthesis. Effects of zinc ions resembled those of cadmium ions on the E. Proteomic Profiling of Escherichia Coli in Response to Heavy Metals Stress 680 coli metabolism and energy production. Cysteine synthase A and zinc-binding transport protein (ZnuA) were up-regulated upon exposure to copper and mercury, respectively. Taken together, it can be proposed that once the growth arrestment by toxic metals occurred, various mechanisms, i) up-regulating of some enzymes involved in catabolic regulation to maintain cellular energy production; ii) initiation of using the low-energy requiring transport system for importing of amino acid and other carbon sources; iii) facilitating synthesis of metal-binding amino acids and iv) enhancing metal-transporting system for intracellular metal regulation, are accounted for the adaptation and cellular compensation.