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Crystal Structure Of Mycobacterium Tuberculosis Alkylperoxidase Ahpd H137F mutant
Structural highlights
FunctionAHPD_MYCTU Antioxidant protein with alkyl hydroperoxidase activity. Required for the reduction of the AhpC active site cysteine residues and for the regeneration of the AhpC enzyme activity.[1] [2] [3] Together with AhpC, DlaT and Lpd, constitutes an NADH-dependent peroxidase active against hydrogen and alkyl peroxides as well as serving as a peroxynitrite reductase, thus protecting the bacterium against reactive nitrogen intermediates and oxidative stress generated by the host immune system.[4] [5] [6] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedAhpD, a protein with two cysteine residues, is required for physiological reduction of the Mycobacterium tuberculosis alkylhydroperoxidase AhpC. AhpD also has an alkylhydroperoxidase activity of its own. The AhpC/AhpD system provides critical antioxidant protection, particularly in the absence of the catalase-peroxidase KatG, which is suppressed in most isoniazid-resistant strains. Based on the crystal structure, we proposed recently a catalytic mechanism for AhpD involving a proton relay in which the Glu118 carboxylate group, via His137 and a water molecule, deprotonates the catalytic residue Cys133 (Nunn, C. M., Djordjevic, S., Hillas, P. J., Nishida, C., and Ortiz de Montellano, P. R. (2002) J. Biol. Chem. 277, 20033-20040). A possible role for His132 in subsequent formation of the Cys133-Cys130 disulfide bond was also noted. To test this proposed mechanism, we have expressed the H137F, H137Q, H132F, H132Q, E118F, E118Q, C133S, and C130S mutants of AhpD, determined the crystal structures of the H137F and H132Q mutants, estimated the pKa values of the cysteine residues, and defined the kinetic properties of the mutant proteins. The collective results strongly support the proposed catalytic mechanism for AhpD. The mechanism of Mycobacterium tuberculosis alkylhydroperoxidase AhpD as defined by mutagenesis, crystallography, and kinetics.,Koshkin A, Nunn CM, Djordjevic S, Ortiz de Montellano PR J Biol Chem. 2003 Aug 8;278(32):29502-8. Epub 2003 May 21. PMID:12761216[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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