tailieunhanh - Báo cáo khoa học: Guanidinium chloride- and urea-induced unfolding of FprA, a mycobacterium NADPH-ferredoxin reductase Stabilization of an apo-protein by GdmCl

The guanidinium chloride- and urea-induced unfolding of FprA, a mycobacterium NADPH-ferredoxin reductase, was examined in detail using multiple spectroscopic techniques, enzyme activity measurements and size exclusion chromatography. The equilibrium unfolding of FprA by urea is a cooperative process where no stabilization of any partially folded inter-mediate of protein is observed. In comparison, the unfolding of FprA by guanidinium chloride proceeds through intermediates that are stabilized by interaction of protein with guanidinium chloride. . | iFEBS Journal Guanidinium chloride- and urea-induced unfolding of FprA a mycobacterium NADPH-ferredoxin reductase Stabilization of an apo-protein by GdmCl Nidhi Shukla1 Anant Narayan Bhatt1 Alessandro Aliverti2 Giuliana Zanetti2 and Vinod Bhakuni1 1 Division of Molecular and StructuralBiology CentralDrug Research Institute Lucknow India 2 Dipartimento Di Scienze Biomolecolarie e Biotechnologie Universita degli Studi di Milano Milano Italy Keywords circular dichroism electrostatic inteaction fluorescence FprA chloride intermediates Correspondence V. Bhakuni Division of Molecular and StructuralBiology CentralDrug Research Institute Lucknow 226 001 India Fax 91 522 223405 E-mail bhakuniv@ Note This is CDRI communication number 6706. Received 10 January 2005 revised 22 February 2005 accepted 7 March 2005 doi The guanidinium chloride- and urea-induced unfolding of FprA a mycobacterium NADPH-ferredoxin reductase was examined in detail using multiple spectroscopic techniques enzyme activity measurements and size exclusion chromatography. The equilibrium unfolding of FprA by urea is a cooperative process where no stabilization of any partially folded intermediate of protein is observed. In comparison the unfolding of FprA by guanidinium chloride proceeds through intermediates that are stabilized by interaction of protein with guanidinium chloride. In the presence of low concentrations of guanidinium chloride the protein undergoes compaction of the native conformation this is due to optimization of charge in the native protein caused by electrostatic shielding by the guanidinium cation of charges on the polar groups located on the protein side chains. At a guanidinium chloride concentration of about M stabilization of apo-protein was observed. The stabilization of apo-FprA by guanidinium chloride is probably the result of direct binding of the Gdm cation to protein. The results presented here suggest that the difference .