Crystal Structure of AhpE from Mycobacterium tuberculosis, a 1-Cys peroxiredoxin.
All 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.
Li
Simon
S
Centre of Molecular Biodiscovery, University of Auckland, Auckland, New Zealand.
Peterson
Neil A
NA
Kim
Min-Young
MY
Kim
Chang-Yub
CY
Hung
Li-Wei
LW
Yu
Minmin
M
Lekin
Timothy
T
Segelke
Brent W
BW
Lott
J Shaun
JS
Baker
Edward N
EN
D000595:Amino Acid Sequence; D001665:Binding Sites; D001965:Bromides / Q000494:pharmacology; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D010544:Peroxidases / Q000737:chemistry* / Q000378:metabolism; D054464:Peroxiredoxins; D011485:Protein Binding; D020836:Protein Structure, Quaternary / Q000187:drug effects; D016415:Sequence Alignment
D001965:Bromides; D010544:Peroxidases; D054464:Peroxiredoxins