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Publication Abstract from PubMed

The mycobacterial enzyme Rv1284 is a member of the beta-carbonic anhydrase family that has been deemed essential for survival of the pathogen. The active site cavity of this dimeric protein is characterised by an exceptionally small volume and harbours a catalytic zinc ion coordinated by two cysteine and one histidine residue side chains. Using the natural products polycarpine and emodin as chemical probes in crystallographic experiments and stopped-flow enzyme assays, we describe here that the catalytic activity can be reversibly inhibited by oxidation. Oxidative conditions lead to removal of one of the active site cysteine residues from the coordination sphere of the catalytic metal ion by engagement in a disulphide bond with another cysteine residue close by. The subsequent loss of the metal ion, which is supported by crystallographic analysis, may thus render the protein catalytically inactive. The oxidative inhibition of Rv1284 can be reversed by exposing the protein to reducing conditions. Since the physical size of the chemical probes used in this study substantially exceeds the active site volume, we hypothesised that these compounds exert their effects from a surface-bound location and identified tyrosine 120 as a critical residue for oxidative inactivation. These findings link conditions of oxidative stress to pH homeostasis of the pathogen. Since oxidative stress and acidification are defence mechanisms employed by the innate immune system of the host, we suggest that Rv1284 may be a component of the mycobacterial survival strategy. This article is protected by copyright. All rights reserved.

Chemical probing suggests Redox-regulation of the carbonic anhydrase activity of mycobacterial Rv1284.,Nienaber L, Cave-Freeman E, Cross M, Mason L, Bailey UM, Amani P, Davis R, Taylor P, Hofmann A FEBS J. 2015 Apr 30. doi: 10.1111/febs.13313. PMID:25929542^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.