Role of alkyl hydroperoxide reductase subunit C (AhpC) as a peroxiredoxin in Leptospira interro-gans against oxidative stress / 中华微生物学和免疫学杂志

Objective To analyze the enzymatic properties of alkyl hydroperoxide reductase sub-unit C (AhpC) from Leptospira interrogans (L.interrogans) and to elucidate its physiological roles in host-pathogen interactions in macrophages during Leptospira infection. Methods A prokaryotic expression system for ahpC gene of L.interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai was established to ex-press the recombinant AhpC(rAhpC). After purified by Ni-NTA affinity chromatography,the enzymatic ac-tivity of the rAhpC and its role in protecting DNA from oxidation were analyzed. The importance of each cys-teine in its molecule was evaluated through site-directed mutation. L.interrogans strains were pretreated with or without Conoidin A, a covalent inhibitor of peroxiredoxin, and then were used to infect macrophages. Changes in oxidative status in leptospires and survival rates of L.interrogans strains were analyzed by fluores-cence-activated cell sorting and colony counting method. Results The rAhpC was successfully expressed in the established prokaryotic expression system. It had peroxiredoxin activity that was able to catalyze the re-duction of hydrogen peroxide. Its ability of reducing hydrogen peroxide depended on the thioredoxin/thiore-doxin reductase system. Cys47 (a peroxidatic cysteine) and Cys167 (a resolving cysteine) were critical to maintaining the enzymatic activity of AhpC. AhpC could protect DNA from hydrogen peroxide induced-oxida-tive damage. When L.interrogans strains were pretreated with Conoidin A,the oxidative status in leptospires was elevated and the survival of L.interrogans in macrophages was significantly reduced in a dose-dependent manner. Conclusion The AhpC of L.interrogans is a thioredoxin-dependent peroxiredoxin that plays an im-portant role in protecting L.interrogans against oxidative stress in macrophages.

Cloning and expression of H.pylori ahpC in prokaryotic expression vector / 西安交通大学学报(医学版)

Objective To construct a prokaryotic expression system of ahpC gene of Helicobacter pylori. Methods The ahpC gene was amplified from Hp chromosomal DNA by PCR technique and cloned into the expression vector pET-30a. The recombinant vector pET30a-ahpC was identified by DNA sequencing and transformed to E.coli BL21 (DE3) for expression under induction by IPTG. The expression product was analyzed by SDS-PAGE. Results PCR product showed that ahpC gene consisted of 594bp. The gene fragment that was inserted into the recombinant vector was identified to GenBank for 99%. SDS-PAGE showed that the induced protein was expressed highly in the host bacterium. Conclusion A prokaryotic high-expression system for ahpC gene has been successfully constructed. It can highly express r-AhpC protein in E.coli.