Molecular characterization of Mycobacterium tuberculosis cystathionine gamma synthase--apo- and holoforms.

Multiple probes like absorbance, circular dichroism, fluorescence and biochemical changes have been exploited to understand the role of PLP (pyridoxal 5' phosphate) in guanidine hydrochloride (GdnHCl) mediated unfolding and refolding processes of cystathionine gamma synthase from Mycobacterium tuberculosis (MtCGS). Unfolding by GdnHCl inactivates the enzyme due to loss of ketoenamine tautomer. Though PLP induces difference in secondary structure content, it is unable to provide stabilizing effect during the overall secondary structure unfolding process. But it induces tertiary structure stability of the protein thereby counteracting the deleterious effect of denaturant. In silico modelling and cofactor docking provide insights into molecular structure of the enzyme.