Liochev S I, Fridovich I
Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710.
J Biol Chem. 1991 May 15;266(14):8747-50.
Gross overproduction of the manganese-containing superoxide dismutase in Escherichia coli, by virtue of a multicopy plasmid bearing the sodA gene, decreases enumeration on paraquat-containing agar plates. This reflects growth inhibition, not lethality, since cells on these plates can be rescued by exclusion of dioxygen. Growth in liquid medium revealed that the control strain adapted to growth in the presence of paraquat more rapidly than did the overproducer. Glucose-6-phosphate dehydrogenase, taken as a representative of the superoxide-inducible soxR regulon, was induced during exposure to paraquat to a much greater extent in the control than in the superoxide dismutase-over-producing strain. These results support the view that overproduction of superoxide dismutase interferes with induction of the soxR regulon and thus prevents a balanced adaptation to the multiple aspects of the toxicity of aerobic paraquat.
通过携带sodA基因的多拷贝质粒，在大肠杆菌中大量过量生产含锰超氧化物歧化酶，会减少在含百草枯的琼脂平板上的菌落计数。这反映的是生长抑制，而非致死性，因为这些平板上的细胞可通过排除双氧基而得到挽救。液体培养基中的生长情况表明，对照菌株比过量生产者更快适应在百草枯存在下的生长。作为超氧化物诱导型soxR调节子代表的葡萄糖-6-磷酸脱氢酶，在暴露于百草枯期间，在对照菌株中的诱导程度比在超氧化物歧化酶过量生产菌株中要大得多。这些结果支持这样一种观点，即超氧化物歧化酶的过量生产会干扰soxR调节子的诱导，从而阻止对需氧百草枯毒性多方面的平衡适应。
