Structural and mechanistic insights into type II trypanosomatid tryparedoxin-dependent peroxidases.
TbTDPX (Trypanosoma brucei tryparedoxin-dependent peroxidase) is a genetically validated drug target in the fight against African sleeping sickness. Despite its similarity to members of the GPX (glutathione peroxidase) family, TbTDPX2 is functional as a monomer, lacks a selenocysteine residue and relies instead on peroxidatic and resolving cysteine residues for catalysis and uses tryparedoxin rather than glutathione as electron donor. Kinetic studies indicate a saturable Ping Pong mechanism, unlike selenium-dependent GPXs, which display infinite K(m) and V(max) values. The structure of the reduced enzyme at 2.1 A (0.21 nm) resolution reveals that the catalytic thiol groups are widely separated [19 A (0.19 nm)] and thus unable to form a disulphide bond without a large conformational change in the secondary-structure architecture, as reported for certain plant GPXs. A model of the oxidized enzyme structure is presented and the implications for small-molecule inhibition are discussed.
Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
Magnus S
MS
Alphey
Janine
J
König
Alan H
AH
Fairlamb
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010544:Peroxidases / Q000737:chemistry* / Q000378:metabolism; D015800:Protozoan Proteins / Q000737:chemistry* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D014346:Trypanosoma brucei brucei / Q000201:enzymology*
D015800:Protozoan Proteins; D011994:Recombinant Proteins; D010544:Peroxidases; C110959:tryparedoxin peroxidase