Differential chemical and thermal unfolding pattern of Rv3588c and Rv1284 of Mycobacterium tuberculosis - A comparison by fluorescence and circular dichroism spectroscopy

The thermal and chemical unfolding pathways of two beta carbonic anhydrases, Rv3588c and Rv1284 of Mycobacterium tuberculosis have been compared by fluorescence and circular dichroism. Chemical and thermal denaturation of the tertiary and secondary structures of these two ubiquitous enzymes of the pathogen reveals that the unfolding of Rv3588c is mediated through the formation of a molten globule intermediate with depleted tertiary structure. However, Rv1284 directly unfolds from the native to the unfolded state. Calculation of the thermodynamic parameters suggest that overall Rv3588c is more stable than Rv1284. Stern-Volmer analysis together with the fluorescence spectra of the proteins suggest that Trp-115 in Rv1284 is more buried than Trp10 in Rv3588c. The tryptophan residues in both the proteins are surrounded by positively charged amino acid residues. (C) 2009 Elsevier B.V. All rights reserved.