Functional and structural characterization of a thiol peroxidase from Mycobacterium tuberculosis.
A thiol peroxidase (Tpx) from Mycobacterium tuberculosis was functionally analyzed. The enzyme shows NADPH-linked peroxidase activity using a thioredoxin-thioredoxin reductase system as electron donor, and anti-oxidant activity in a thiol-dependent metal-catalyzed oxidation system. It reduces H2O2, t-butyl hydroperoxide, and cumene hydroperoxide, and is inhibited by sulfhydryl reagents. Mutational studies revealed that the peroxidatic (Cys60) and resolving (Cys93) cysteine residues are critical amino acids for catalytic activity. The X-ray structure determined to a resolution of 1.75 A shows a thioredoxin fold similar to that of other peroxiredoxin family members. Superposition with structural homologues in oxidized and reduced forms indicates that the M. tuberculosis Tpx is a member of the atypical two-Cys peroxiredoxin family. In addition, the short distance that separates the Calpha atoms of Cys60 and Cys93 and the location of these cysteine residues in unstructured regions may indicate that the M. tuberculosis enzyme is oxidized, though the side-chain of Cys60 is poorly visible. It is solely in the reduced Streptococcus pneumoniae Tpx structure that both residues are part of two distinct helical segments. The M. tuberculosis Tpx is dimeric both in solution and in the crystal structure. Amino acid residues from both monomers delineate the active site pocket.
Rho
Beom-Seop
BS
Bioscience Division, MS M888, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Hung
Li-Wei
LW
Holton
James M
JM
Vigil
Dominico
D
Kim
Su-Il
SI
Park
Min S
MS
Terwilliger
Thomas C
TC
Pédelacq
Jean-Denis
JD
D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000378:metabolism; D019281:Dimerization; D008969:Molecular Sequence Data; D008970:Molecular Weight; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry* / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D012694:Serine / Q000378:metabolism; D012996:Solutions
D050505:Mutant Proteins; D012996:Solutions; D012694:Serine; D009249:NADP; D010544:Peroxidases; C058652:thiol-dependent peroxidase; D003545:Cysteine