5id2 | pdb_00005id2
Asymmetry in the active site of Mycobacterium tuberculosis AhpE upon exposure to Mycothiol
Structural highlights
FunctionAHPE_MYCTU Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. Plays a role in cell protection against oxidative stress by detoxifying peroxides. May represent an important antioxidant defense against cytotoxic peroxides, especially peroxynitrite, which can be formed by activated macrophages during infection.[1] [2] Publication Abstract from PubMedMycobacterium 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 (MtAhpE), and defined as a potential tuberculosis drug target. The reduced MtAhpE (MtAhpE-SH) scavenges peroxides to become converted to MtAhpE-SOH. To provide continuous availability of MtAhpE-SH, MtAhpE-SOH has to become reduced. Here, we used NMR spectroscopy to delineate the reduced (MtAhpE-SH), sulphenic (MtAhpE-SOH) and sulphinic (MtAhpE-SO2H) states of MtAhpE through cysteinyl-labelling, and provide for the first time evidence of a mycothiol-dependent mechanism of MtAhpE reduction. This is confirmed by crystallographic studies, wherein MtAhpE was crystallised in the presence of mycothiol and the structure was solved at 2.43A resolution. Combined with NMR-studies, the crystallographic structures reveal conformational changes of important residues during the catalytic cycle of MtAhpE. 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 MtAhpE necessary for activity, being also discussed in the context of concerted substrate binding inside the dimeric MtAhpE. Redox chemistry of Mycobacterium tuberculosis alkylhydroperoxide reductase E (AhpE): Structural and mechanistic insight into a mycoredoxin-1 independent reductive pathway of AhpE via mycothiol.,Kumar A, Balakrishna AM, Nartey W, Manimekalai MS, Gruber G Free Radic Biol Med. 2016 Jul 11. pii: S0891-5849(16)30327-6. doi:, 10.1016/j.freeradbiomed.2016.07.007. PMID:27417938[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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