The Solution Structure of the Lipoyl Acid-Bearing Domain of Human Mitochondrial Branched-Chain alpha-Ketoacid Dehydrogenase.


Chi-Fon Chang1, Hui-Ting Chou2, Oksana Gorbatyuk1, Jacinta L. Chuang3, David Chuang3 and Tai-huang Huang1,2

1Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei, Taiwan

2 Department of Physics, National Taiwan University

3Dept. Biochemistry, U. of Texas Southwestern Medical Center, Dallas, TX, USA.


Di-domain of the transacylase component (E2) of human mitochondrial branched-chain alpha-ketoacid dehydrogenase (BCKD) complex comprises an N-terminal lipoyl acid-bearing domain (LBD) and a downstream component-binding domain (CBD), connected by a flexible linker region.  The di-domain sequences contain the sites of known human mutations that cause inherited maple syrup disease.  Structure of the di-domain will provide important insights into specific protein-protein interaction as well as catalytic mechanism of the mammalian BCKD complex. We have applied multidimensional heteronuclear NMR spectroscopy to determine the solution structure of LBD. Good quality structure was obtained using partially assigned NOEs, combine with automatically derived restraints from ARIA (Ambiguous Restraints for Iterative Assignment). The structure of LBD domain was found to contain two four-stranded beta-sheets forming a flattened beta-barrel. The lipoylation site, K44, resides at the turn connecting the two beta-strands and is exposed to the solvent.  Structure comparison of the LBD domain from other different sources will be discussed.