부산대학교 도서관

Mycobacterium tuberculosis ( Mtb ) has the ability to persist within the human host for a long time in a dormant stage and re-merges when the immune system is compromised. The pathogenic bacterium employs an elaborate antioxidant defence machinery composed of the mycothiol- and thioredoxin system in addition to a superoxide dismutase, a catalase, and peroxiredoxins (Prxs). Among the family of Peroxiredoxins, Mtb expresses a 1-cysteine peroxiredoxin, known as alkylhydroperoxide reductase E ( Mt AhpE), and defined as a potential tuberculosis drug target. The reduced Mt AhpE ( Mt AhpE-SH) scavenges peroxides to become converted to Mt AhpE-SOH. To provide continuous availability of Mt AhpE-SH, Mt AhpE-SOH has to become reduced. Here, we used NMR spectroscopy to delineate the reduced ( Mt AhpE-SH), sulphenic ( Mt AhpE-SOH) and sulphinic ( Mt AhpE-SO 2 H) states of Mt AhpE through cysteinyl-labelling, and provide for the first time evidence of a mycothiol-dependent mechanism of Mt AhpE reduction. This is confirmed by crystallographic studies, wherein Mt AhpE was crystallized in the presence of mycothiol and the structure was solved at 2.43 Å resolution. Combined with NMR-studies, the crystallographic structures reveal conformational changes of important residues during the catalytic cycle of Mt AhpE. In addition, alterations of the overall protein in solution due to redox modulation are observed by small angle X-ray scattering (SAXS) studies. Finally, by employing SAXS and dynamic light scattering, insight is provided into the most probable physiological oligomeric state of Mt AhpE necessary for activity, being also discussed in the context of concerted substrate binding inside the dimeric Mt AhpE. [ABSTRACT FROM AUTHOR]