Spectroscopic Studies of the Folding of Lipoyl Acid-Bearing Domain of Human Mitochondrial Branched-Chain alpha-Ketoacid Dehydrogenase


Yu-Chu Chang1, Mandar T. Naik2, Tai-Huang Huang1,2

1Deapartment of Physics, National Taiwan University, Taipei, Taiwan

2Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan


Lipoyl Acid-Bearing Domain (LBD) is a small domain within the human mitochondrial Branched-Chain alpha-Ketoacid Dehydrogenase complex (BCKD). This huge complex contains three major enzymes: E1, E2, and E3.  LBD is a domain of the E2 (drolipoyltransferase) component and mutations in the E2 component are responsible for the inherited maple syrup urine disease. We have employed Circular Dichroism Spectroscopy (CD) to study the folding/unfolding process of LBD. The CD spectrum of LBD showed two pronounced peaks at 228 nm and 203 nm, indicating that LBD contains a β-barrel structure. This result is consistent with our NMR structure study, which showed that LBD folds into a flatted β-barrel. We have performed spectroscopic studies on temperature, urea and guanidine hydrochloride denature of LBD. LBD unfold reversibly under these denaturation conditions. The results of these studies will be presented.