title: Solution structure and dynamics of the lipoic acid-bearing domain of human mitochondrial branched-chain alpha-keto acid dehydrogenase complex.
abstract: The lipoyl-bearing domain (LBD) of the transacylase (E2) subunit of the branched-chain alpha-keto acid dehydrogenase complex plays a central role in substrate channeling in this mitochondrial multienzyme complex. We have employed multidimensional heteronuclear NMR techniques to determine the structure and dynamics of the LBD of the human branched-chain alpha-keto acid dehydrogenase complex (hbLBD). Similar to LBD from other members of the alpha-keto acid dehydrogenase family, the solution structure of hbLBD is a flattened beta-barrel formed by two four-stranded antiparallel beta-sheets. The lipoyl Lys(44) residue resides at the tip of a beta-hairpin comprising a sharp type I beta-turn and the two connecting beta-strands 4 and 5. A prominent V-shaped groove formed by a surface loop, L1, connecting beta 1- and beta 2-strands and the lipoyl lysine beta-hairpin constitutes the functional pocket. We further applied reduced spectral density functions formalism to extract dynamic information of hbLBD from (15)N-T(1), (15)N-T(2), and ((1)H-(15)N) nuclear Overhauser effect data obtained at 600 MHz. The results showed that residues surrounding the lipoyl lysine region comprising the L1 loop and the Lys(44) beta-turn are highly flexible, whereas beta-sheet S1 appears to display a slow conformational exchange process.
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan 11529, Republic of China.
authors.forename: Chi-Fon
authors.initials: CF
authors.lastname: Chang
authors.forename: Hui-Ting
authors.initials: HT
authors.lastname: Chou
authors.forename: Jacinta L
authors.initials: JL
authors.lastname: Chuang
authors.forename: David T
authors.initials: DT
authors.lastname: Chuang
authors.forename: Tai-Huang
authors.initials: TH
authors.lastname: Huang
mesh_terms: D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D001665:Binding Sites; D003001:Cloning, Molecular; D004926:Escherichia coli; D006801:Humans; D007658:Ketone Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology*; D008958:Models, Molecular; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012996:Solutions; D008063:Thioctic Acid / Q000378:metabolism*
chemical_list: D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D012996:Solutions; D008063:Thioctic Acid; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)