1dci: Difference between revisions

BACKGROUND: The degradation of unsaturated fatty acids is vital to all, living organisms. Certain unsaturated fatty acids must be catabolized via, a pathway auxiliary to the main beta-oxidation pathway. Dienoyl-coenzyme A, (dienoyl-CoA) isomerase catalyzes one step of this auxiliary pathway, the, isomerization of 3-trans,5-cis-dienoyl-CoA to 2-trans,4-trans-dienoyl-CoA, and is imported into both mitochondria and peroxisomes. Dienoyl-CoA, isomerase belongs to a family of CoA-binding proteins that share the, enoyl-CoA hydratase/isomerase sequence motif. RESULTS: The crystal, structure of rat dienoyl-CoA isomerase has been determined at 1.5 A, resolution. The fold closely resembles that of enoyl-CoA hydratase and, 4-chlorobenzoyl-CoA dehalogenase. Dienoyl-CoA isomerase forms hexamers, made up of two trimers. The structure contains a well ordered peroxisomal, targeting signal type-1 which is mostly buried in the inter-trimer space., The active-site pocket is deeply buried and entirely hydrophobic, with the, exception of the acidic residues Asp176, Glu196 and Asp204. Site-directed, mutagenesis of Asp204 revealed that this residue is essential for, catalysis. In a molecular modeling simulation, a molecule of, 3-trans,5-cis-octadienoyl-CoA was docked into the active site., CONCLUSIONS: The structural data, supported by the mutagenesis data, suggest a reaction mechanism where Glu196 acts as a proton acceptor and, Asp204 acts as a proton donor. Asp176 is paired with Glu196 and is, important for optimizing the catalytic proton transfer properties of, Glu196. In the predicted mode of substrate binding, an oxyanion hole, stabilizes the transition state by binding the thioester oxygen. The, presence of a buried peroxisomal targeting signal suggests that, dienoyl-CoA isomerase is prevented from reaching its hexameric structure, in the cytosol.

1DCI is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus] with SO4, MG and EDO as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Enoyl-CoA_hydratase Enoyl-CoA hydratase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.2.1.17 4.2.1.17] Structure known Active Site: . Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1DCI OCA].  

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