Characterization of the Mycobacterium tuberculosis H37Rv alkyl hydroperoxidase AhpC points to the importance of ionic interactions in oligomerization and activity.

Chauhan, Radha and Mande, S C (2001) Characterization of the Mycobacterium tuberculosis H37Rv alkyl hydroperoxidase AhpC points to the importance of ionic interactions in oligomerization and activity. The Biochemical journal, 354 (Pt 1). pp. 209-15. ISSN 0264-6021

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Abstract

An alkyl hydroperoxidase (AhpC) has been found frequently to be overexpressed in isoniazid-resistant strains of Mycobacterium tuberculosis. These strains have an inactivated katG gene encoding a catalase peroxidase, which might render mycobacteria susceptible to the toxic peroxide radicals, thus leading to the concomitant overexpression of the AhpC. Although the overexpressed AhpC in isoniazid-resistant strains of M. tuberculosis may not directly participate in isoniazid action, AhpC might still assist M. tuberculosis in combating oxidative damage in the absence of the catalase. Here we have attempted to characterize the AhpC protein biochemically and report its functional and oligomerization properties. The alkyl hydroperoxidase of M. tuberculosis is unique in many ways compared with its well-characterized homologues from enteric bacteria. We show that AhpC is a decameric protein, composed of five identical dimers held together by ionic interactions. Dimerization of individual subunits takes place through an intersubunit disulphide linkage. The ionic interactions play a significant role in enzymic activity of the AhpC protein. The UV absorption spectrum and three-dimensional model of AhpC suggest that interesting conformational changes may take place during oxidation and reduction of the intersubunit disulphide linkage. In the absence of the partner AhpF subunit in M. tuberculosis, the mycobacterial AhpC might use small-molecule reagents, such as mycothiol, for completing its enzymic cycle.

Item Type: Article
Additional Information: Copyright of this article belongs to Portland Press.
Uncontrolled Keywords: decamer, DTT oxidation, mycothiol, peroxidase, thioredoxin
Subjects: Q Science > QD Chemistry
Depositing User: Dr. K.P.S.Sengar
Date Deposited: 04 Jan 2012 14:57
Last Modified: 29 Mar 2012 07:28
URI: http://crdd.osdd.net/open/id/eprint/303

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