title: Cyclosporin A binding to Mycobacterium tuberculosis peptidyl-prolyl cis-trans isomerase A--investigation by CD, FTIR and fluorescence spectroscopy.
abstract: Circular dichroism and resolution-enhanced Fourier transform infrared reveal induction of secondary structural elements on peptidyl-prolyl cis-trans isomerase A (PpiA) from Mycobacterium tuberculosis upon binding cyclosporin A (CsA). Thermal denaturation shows aggregation of PpiA at higher temperatures (>70 degrees C) and CsA fails to impart stabilization in protein structure. However, CsA stabilizes PpiA structure in urea denaturation. In presence/absence of CsA, urea-induced reversible unfolding of secondary and tertiary structures follows two-state and three-state transition, respectively. The chemical unfolding results also demonstrate that loss in the tertiary structure precedes the loss in secondary structure both in presence and absence of CsA at the initial stages. Fluorescence quenching suggests presence of a positive barrier around tryptophan microenvironment of PpiA.
authors.affiliation: Department of Biotechnology, Indian Institute of Technology, Kharagpur, West Bengal--721302, India.
authors.forename: Devrani
authors.initials: D
authors.lastname: Mitra
authors.forename: Somnath
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Das
mesh_terms: D002942:Circular Dichroism; D016572:Cyclosporine / Q000494:pharmacology*; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000201:enzymology*; D019696:Peptidylprolyl Isomerase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011489:Protein Denaturation; D017510:Protein Folding; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D016572:Cyclosporine; D019696:Peptidylprolyl Isomerase