title: A two-domain structure of one subunit explains unique features of eukaryotic hydratase 2.
abstract: 2-Enoyl-CoA hydratase 2, a part from multifunctional enzyme type 2, hydrates trans-2-enoyl-CoA to 3-hydroxyacyl-CoA in the (3R)-hydroxy-dependent route of peroxisomal beta-oxidation of fatty acids. Unliganded and (3R)-hydroxydecanoyl coenzyme A-complexed crystal structures of 2-enoyl-CoA hydratase 2 from Candida tropicalis multifunctional enzyme type 2 were solved to 1.95- and 2.35-A resolution, respectively. 2-Enoyl-CoA hydratase 2 is a dimeric, alpha+beta protein with a novel quaternary structure. The overall structure of the two-domain subunit of eukaryotic 2-enoyl-CoA hydratase 2 resembles the homodimeric, hot dog fold structures of prokaryotic (R)-specific 2-enoyl-CoA hydratase and beta-hydroxydecanoyl thiol ester dehydrase. Importantly, though, the eukaryotic hydratase 2 has a complete hot dog fold only in its C-domain, whereas the N-domain lacks a long central alpha-helix, thus creating space for bulkier substrates in the binding pocket and explaining the observed difference in substrate preference between eukaryotic and prokaryotic enzymes. Although the N- and C-domains have an identity of <10% at the amino acid level, they share a 50% identity at the nucleotide level and fold similarly. We suggest that a subunit of 2-enoyl-CoA hydratase 2 has evolved via a gene duplication with the concomitant loss of one catalytic site. The hydrogen bonding network of the active site of 2-enoyl-CoA hydratase 2 resembles the active site geometry of mitochondrial (S)-specific 2-enoyl-CoA hydratase 1, although in a mirror image fashion. This arrangement allows the reaction to occur by similar mechanism, supported by mutagenesis and mechanistic studies, although via reciprocal stereochemistry.
authors.affiliation: Department of Biochemistry and Biocenter Oulu, University of Oulu, P. O. Box 3000, FIN-90014 University of Oulu, Finland.
authors.forename: M Kristian
authors.initials: MK
authors.lastname: Koski
authors.forename: Antti M
authors.initials: AM
authors.lastname: Haapalainen
authors.forename: J Kalervo
authors.initials: JK
authors.lastname: Hiltunen
authors.forename: Tuomo
authors.initials: T
authors.lastname: Glumoff
mesh_terms: D000214:Acyl Coenzyme A / Q000737:chemistry; D000595:Amino Acid Sequence; D001665:Binding Sites; D041022:Candida tropicalis / Q000201:enzymology; D002384:Catalysis; D020134:Catalytic Domain; D004746:Enoyl-CoA Hydratase / Q000737:chemistry*; D005227:Fatty Acids / Q000378:metabolism; D006860:Hydrogen Bonding; D008024:Ligands; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011485:Protein Binding; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013237:Stereoisomerism
chemical_list: D000214:Acyl Coenzyme A; D005227:Fatty Acids; D008024:Ligands; C060624:3-hydroxydecanoyl-coenzyme A; D004746:Enoyl-CoA Hydratase; C083735:long-chain-enoyl-CoA hydratase