MOLECULAR FEATURES AND PROPERTIES OF MYCOBACTERIAL PROTEINS LINKED TO TUBERCULOSIS PATHOGENESIS

Abstract: The Mycobacterium tuberculosis genome codes for 11 pairs of CFP-10/ESAT-6 proteins (Esx family) as well as the apparatus required for secretion of these proteins. The core machinery for the secretion of ESAT-6 and CFP-10 is encoded by their surrounding genes. Recent studies also identified a distant region, the Rv3612c-Rv3616c operon, which is essential for the CFP-10/ESAT-6 secretion. Constructs carrying Rv3613c, Rv3614c, Rv3615c and Rv3616c coding regions were produced and used to express the corresponding proteins. However, only Rv3614c and Rv3615c were expressed using an E. coli-based expression system. Analysis using a range of spectroscopic techniques on the purified proteins revealed that both Rv3615c and Rv3614c contain stable secondary structure, but little if any stable tertiary structure and exist in a molten globule-like state. This suggests the proteins probably undergo folding upon binding with possible functional partners. Yeast-two hybrid studies showed no intermolecular interaction between the proteins encoded by the Rv3616c-Rv3612c operon, perhaps suggesting the formation of a higher order multi-protein complex