title: Expression and purification of His-tagged rat mitochondrial short-chain 3-hydroxyacyl-CoA dehydrogenase wild-type and Ser137 mutant proteins.
abstract: Mitochondrial 3-hydroxyacyl-CoA dehydrogenase is a key enzyme in the beta-oxidation of fatty acids. The deficiency of this enzyme in patients has been previously reported. We cloned the gene of rat mitochondrial 3-hydroxyacyl-CoA dehydrogenase in a bacterial expression vector pLM1 with six continuous histidine codons attached to the 5' of the gene. The cloned gene was overexpressed in Escherichia coli and the soluble protein was purified with a nickel HiTrap chelating metal affinity column to apparent homogeneity. The specific activity of the purified His-tagged rat mitochondrial 3-hydroxyacyl-CoA dehydrogenase was 452 U/mg. Ser137 is a highly conserved amino acid, which, it has been suggested, is an important residue because of its proximity to the modeled L-3-hydroxyacyl-CoA substrate in the crystal structure of 3-hydroxyacyl-CoA dehydrogenase. We constructed three mutant expression plasmids of the enzyme using site-directed mutagenesis. Mutant proteins were overexpressed in E. coli and purified with a nickel metal affinity column. Kinetic studies of wild-type and mutant proteins were carried out, and the result confirmed that Ser137 is a very important residue of rat mitochondrial 3-hydroxyacyl-CoA dehydrogenase. Our overexpression in E. coli and one-step purification of the highly active rat mitochondrial 3-hydroxyacyl-CoA dehydrogenase greatly facilitated our further investigation of this enzyme, and our result from site-directed mutagenesis increased our understanding of 3-hydroxyacyl-CoA dehydrogenase.
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, PR China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Liu
authors.forename: Xiusheng
authors.initials: X
authors.lastname: Chu
authors.forename: Wenhua
authors.initials: W
authors.lastname: Yu
authors.forename: Pingfeng
authors.initials: P
authors.lastname: Li
authors.forename: Ding
authors.initials: D
authors.lastname: Li
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification*; D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology; D008956:Models, Chemical; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009532:Nickel / Q000737:chemistry; D010100:Oxygen / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D013912:Threonine / Q000737:chemistry
chemical_list: D013912:Threonine; D012694:Serine; D009532:Nickel; D015094:3-Hydroxyacyl CoA Dehydrogenases; D003545:Cysteine; D010100:Oxygen