|Journal of Biological Chemistry (2006) 281(11):7526-32|
|Northeast Structural Genomics Consortium|
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3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase is a key enzyme in the ketogenic pathway that supplies metabolic fuel to extrahepatic tissues. ...
Enzyme deficiency may be due to a variety of human mutations and can be fatal. Diminished activity has been explained based on analyses of recombinant human mutant proteins or, more recently, in the context of structural models for the enzyme. We report the experimental determination of a crystal structure at 2.1 A resolution of the recombinant human mitochondrial HMG-CoA lyase containing a bound activator cation and the dicarboxylic acid 3-hydroxyglutarate. The enzyme adopts a (betaalpha)(8) barrel fold, and the N-terminal barrel end is occluded. The structure of a physiologically relevant dimer suggests that substrate access to the active site involves binding across the cavity located at the C-terminal end of the barrel. An alternative hypothesis that involves substrate insertion through a pore proposed to extend through the barrel is not compatible with the observed structure. The activator cation ligands included Asn(275), Asp(42),His(233), and His(235); the latter three residues had been implicated previously as contributing to metal binding or enzyme activity. Arg(41), previously shown to have a major effect on catalytic efficiency, is also located at the active site. In the observed structure, this residue interacts with a carboxyl group of 3-hydroxyglutarate, the hydrolysis product of the competitive inhibitor 3-hydroxyglutaryl-CoA required for crystallization of human enzyme. The structure provides a rationale for the decrease in enzyme activity due to clinical mutations, including H233R, R41Q, D42H, and D204N, that compromise active site function or enzyme stability.
|metabolism pharmacology chemistry urine |
|Crystallography, X-Ray X-Ray Diffraction Glutarates Dimerization Hydrolysis Magnesium Models, Chemical Ligands Ions Protein Folding Substrate Specificity Binding Sites Electrophoresis, Polyacrylamide Gel Amino Acid Sequence Sequence Homology, Amino Acid Cations Serine Models, Molecular Recombinant Proteins Bacillus subtilis Mutation Humans Molecular Sequence Data Enzyme Inhibitors Bacillus Animals Kinetics Mutagenesis Oxo-Acid-Lyases Rats Protein Binding Catalysis |
|21 (Last update: 07/22/2017 11:25:23am)|
|J Biol Chem. 2006 Mar 17;281(11):7526-32. Epub 2005 Dec 5.|