title: The X-ray structure of Escherichia coli enoyl reductase with bound NAD+ at 2.1 A resolution.
abstract: Enoyl acyl carrier protein reductase catalyses the last reductive step of fatty acid biosynthesis, reducing an enoyl acyl carrier protein to an acyl-acyl carrier protein with NAD(P)H as the cofactor. The crystal structure of enoyl reductase (ENR) from Escherichia coli has been determined to 2.1 A resolution using a combination of molecular replacement and isomorphous replacement and refined using data from 10 A to 2.1 A to an R-factor of 0.16. The final model consists of the four subunits of the tetramer, wherein each subunit is composed of 247 of the expected 262 residues, and a NAD+ cofactor for each subunit of the tetramer contained in the asymmetric unit plus a total of 327 solvent molecules. There are ten disordered residues per subunit which form a loop near the nucleotide binding site which may become ordered upon substrate binding. Each monomer is composed of a seven-stranded parallel beta-sheet flanked on each side by three alpha-helices with a further helix lying at the C terminus of the beta-sheet. This fold is highly reminiscent of the Rossmann fold, found in many NAD(P)H-dependent enzymes. Analysis of the sequence and structure of ENR and comparisons with the family of short-chain alcohol dehydrogenases, identify a conserved tyrosine and lysine residue as important for catalytic activity. Modelling studies suggest that a region of the protein surface that contains a number of strongly conserved hydrophobic residues and lies adjacent to the nicotinamide ring, forms the binding site for the fatty acid substrate.
authors.affiliation: Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, The University of Sheffield, UK.
authors.forename: C
authors.initials: C
authors.lastname: Baldock
authors.forename: J B
authors.initials: JB
authors.lastname: Rafferty
authors.forename: A R
authors.initials: AR
authors.lastname: Stuitje
authors.forename: A R
authors.initials: AR
authors.lastname: Slabas
authors.forename: D W
authors.initials: DW
authors.lastname: Rice
mesh_terms: D000426:Alcohol Dehydrogenase / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D001937:Brassica / Q000201:enzymology; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH); D004926:Escherichia coli / Q000201:enzymology*; D064429:Fatty Acid Synthases / Q000737:chemistry* / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000201:enzymology; D009243:NAD / Q000737:chemistry / Q000378:metabolism*; D009711:Nucleotides / Q000378:metabolism; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D017510:Protein Folding; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D005227:Fatty Acids; D009711:Nucleotides; D009243:NAD; D010088:Oxidoreductases; D000426:Alcohol Dehydrogenase; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH); D064429:Fatty Acid Synthases