Enhancing survival of Escherichia coli by expression of azoreductase AZR possessing quinone reductase activity
- 503 Downloads
Quinone reductase activity of azoreductase AZR from Rhodobacter sphaeroides was reported. High homologies were found in the cofactor/substrate-binding regions of quinone reductases from different domains. 3D structure comparison revealed that AZR shared a common overall topology with mammal NAD(P)H/quinone oxidoreductase NQO1. With menadione as substrate, the optimal pH value and temperature were pH 8–9 and 50°C, respectively. Following the ping-pong kinetics, AZR transferred two electrons from NADPH to quinone substrate. It could reduce naphthoquinones and anthraquinones, such as menadione, lawsone, anthraquinone-2-sulfonate, and anthraquinone-2,6-disulfonate. However, no activity was detected with 1,4-benzoquinone. Dicoumarol competitively inhibited AZR’s quinone reductase activity with respect to NADPH, with an obtained Ki value of 87.6 μM. Significantly higher survival rates were obtained in Escherichia coli YB overexpressing AZR than in the control strain when treated by heat shock and oxidative stressors such as H2O2 and menadione.
KeywordsQuinone reductase Azoreductase Oxidative stress Heat shock Survival
- Bradford MM (1976) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem 72:248–254Google Scholar
- Iyanagi T (1987) On the mechanisms of one- and two-electron transfer by flavin enzymes. Chemica Scripta 27A:31–36Google Scholar
- Nicholas KB, Nicholas HB, Jr, Deerfield DW (1997) GeneDoc: analysis and visualization of genetic variation. EMBnet News 4:1–4Google Scholar
- Stolz A (2001) Basic and applied aspects in the microbial degradation of azo dyes. Appl Microbiol Biotechnol 56:69–80Google Scholar