Folding kinetics of the lipoic acid-bearing domain of human mitochondrial branched chain α-ketoacid dehydrogenase complex

A reversible two-step (native state↔denatured state) folding mechanism based on equilibrium and stopped flow experiments is proposed for urea denaturation of the lipoyl-bearing domain (hbLBD) of human mitochondrial branched chain α-ketoacid dehydrogenase (BCKD) complex. The results from this circular dichroism (CD) and fluorescence study have ruled out populated kinetic or equilibrium intermediates on folding pathway of this β-barrel domain under experimental conditions. Both studies suggested mono-exponential kinetics without any burst phases. Moreover the thermodynamic parameters ΔG_H2O and m obtained from the kinetic analysis are consistent with the equilibrium measurements.