1me5
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(New page: 200px<br /><applet load="1me5" size="450" color="white" frame="true" align="right" spinBox="true" caption="1me5, resolution 2.4Å" /> '''Crystal Structure of ...)
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Revision as of 19:14, 20 November 2007
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Crystal Structure of Mycobacterium Tuberculosis Alkylperoxidase AhpD H132Q Mutant
Overview
AhpD, 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.
About this Structure
1ME5 is a Single protein structure of sequence from Mycobacterium tuberculosis. Full crystallographic information is available from OCA.
Reference
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
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