1w6u
Structure of human DECR ternary complex
Structural highlights
DiseaseDECR_HUMAN The protein represented in this entry is involved in disease pathogenesis. A selective decrease in mitochondrial NADP(H) levels due to NADK2 mutations causes a deficiency of NADPH-dependent mitochondrial enzymes, such as DECR1 and AASS.[1] FunctionDECR_HUMAN Auxiliary enzyme of beta-oxidation. It participates in the metabolism of unsaturated fatty enoyl-CoA esters having double bonds in both even- and odd-numbered positions in mitochondria. Catalyzes the NADP-dependent reduction of 2,4-dienoyl-CoA to yield trans-3-enoyl-CoA.[2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedFatty acid catabolism by beta-oxidation mainly occurs in mitochondria and to a lesser degree in peroxisomes. Poly-unsaturated fatty acids are problematic for beta-oxidation, because the enzymes directly involved are unable to process all the different double bond conformations and combinations that occur naturally. In mammals, three accessory proteins circumvent this problem by catalyzing specific isomerization and reduction reactions. Central to this process is the NADPH-dependent 2,4-dienoyl-CoA reductase. We present high resolution crystal structures of human mitochondrial 2,4-dienoyl-CoA reductase in binary complex with cofactor, and the ternary complex with NADP(+) and substrate trans-2,trans-4-dienoyl-CoA at 2.1 and 1.75 A resolution, respectively. The enzyme, a homotetramer, is a short-chain dehydrogenase/reductase with a distinctive catalytic center. Close structural similarity between the binary and ternary complexes suggests an absence of large conformational changes during binding and processing of substrate. The site of catalysis is relatively open and placed beside a flexible loop thereby allowing the enzyme to accommodate and process a wide range of fatty acids. Seven single mutants were constructed, by site-directed mutagenesis, to investigate the function of selected residues in the active site thought likely to either contribute to the architecture of the active site or to catalysis. The mutant proteins were overexpressed, purified to homogeneity, and then characterized. The structural and kinetic data are consistent and support a mechanism that derives one reducing equivalent from the cofactor, and one from solvent. Key to the acquisition of a solvent-derived proton is the orientation of substrate and stabilization of a dienolate intermediate by Tyr-199, Asn-148, and the oxidized nicotinamide. Structure and reactivity of human mitochondrial 2,4-dienoyl-CoA reductase: enzyme-ligand interactions in a distinctive short-chain reductase active site.,Alphey MS, Yu W, Byres E, Li D, Hunter WN J Biol Chem. 2005 Jan 28;280(4):3068-77. Epub 2004 Nov 6. PMID:15531764[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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