title: Guanidine hydrochloride and urea-induced unfolding of Brugia malayi hexokinase.
abstract: Guanidine hydrochloride and urea-induced unfolding of B. malayi hexokinase (BmHk), a tetrameric protein, was examined in detail by using various optical spectroscopic techniques, enzymatic activity measurements, and size-exclusion chromatography. The equilibrium unfolding of BmHk by guanidine hydrochloride (GdmCl) and urea proceeded through stabilization of several unique oligomeric intermediates. In the presence of low concentrations of GdmCl, stabilization of an enzymatically active folded dimer of BmHk was observed. However an enzymatically inactive dimer of BmHk was observed for urea-treated BmHk. This is the first report of an enzymatically active dimer of hexokinase from any human filarial parasite. Furthermore, although complete recovery of the native enzyme was observed on refolding of BmHk samples denatured by use of low concentrations of GdmCl or urea, no recovery of the native enzyme was observed for BmHk samples denatured by use of high concentrations of GdmCl or urea.
authors.affiliation: Division of Biochemistry, Central Drug Research Institute, Lucknow, 226001, UP, India.
authors.forename: Alok Ranjan
authors.initials: AR
authors.lastname: Singh
authors.forename: Shweta
authors.initials: S
authors.lastname: Joshi
authors.forename: Rahul
authors.initials: R
authors.lastname: Arya
authors.forename: Arvind Mohan
authors.initials: AM
authors.lastname: Kayastha
authors.forename: Jitendra Kumar
authors.initials: JK
authors.lastname: Saxena
mesh_terms: D000818:Animals; D017178:Brugia malayi / Q000737:chemistry* / Q000201:enzymology*; D002850:Chromatography, Gel; D002942:Circular Dichroism; D005976:Glutaral / Q000737:chemistry; D019791:Guanidine / Q000737:chemistry*; D015801:Helminth Proteins / Q000737:chemistry*; D006593:Hexokinase / Q000737:chemistry*; D007700:Kinetics; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D055503:Protein Multimerization; D013050:Spectrometry, Fluorescence; D014508:Urea / Q000737:chemistry*
chemical_list: D015801:Helminth Proteins; D014508:Urea; D006593:Hexokinase; D019791:Guanidine; D005976:Glutaral