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The structure of AhpE from Mycobacterium tuberculosis revisitedThe structure of AhpE from Mycobacterium tuberculosis revisited
Structural highlights
Publication Abstract from PubMedAll living systems require protection against the damaging effects of reactive oxygen species. The genome of Mycobacterium tuberculosis, the cause of TB, encodes a number of peroxidases that are thought to be active against organic and inorganic peroxides, and are likely to play a key role in the ability of this organism to survive within the phagosomes of macrophages. The open reading frame Rv2238c in M.tuberculosis encodes a 153-residue protein AhpE, which is a peroxidase of the 1-Cys peroxiredoxin (Prx) family. The crystal structure of AhpE, determined at 1.87 A resolution (R(cryst)=0.179, R(free)=0.210), reveals a compact single-domain protein with a thioredoxin fold. AhpE forms both dimers and octamers; a tightly-associated dimer and a ring-like octamer, generated by crystallographic 4-fold symmetry. In this native structure, the active site Cys45 is in its oxidized, sulfenic acid (S-O-H) state. A second crystal form of AhpE, obtained after soaking in sodium bromide and refined at 1.90 A resolution (R(cryst)=0.242, R(free)=0.286), reveals the reduced structure. In this structure, a conformational change in an external loop, in two of the four molecules in the asymmetric unit, allows Arg116 to stabilise the Cys45 thiolate ion, and concomitantly closes a surface channel. This channel is identified as the likely binding site for a physiological reductant, and the conformational change is inferred to be important for the reaction cycle of AhpE. Crystal Structure of AhpE from Mycobacterium tuberculosis, a 1-Cys peroxiredoxin.,Li S, Peterson NA, Kim MY, Kim CY, Hung LW, Yu M, Lekin T, Segelke BW, Lott JS, Baker EN J Mol Biol. 2005 Mar 4;346(4):1035-46. Epub 2005 Jan 25. PMID:15701515[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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