title: Discovery of the catalytic function of a putative 2-oxoacid dehydrogenase multienzyme complex in the thermophilic archaeon Thermoplasma acidophilum.
abstract: Those aerobic archaea whose genomes have been sequenced possess a single 4-gene operon that, by sequence comparisons with Bacteria and Eukarya, appears to encode the three component enzymes of a 2-oxoacid dehydrogenase multienzyme complex. However, no catalytic activity of any such complex has ever been detected in the Archaea. In the current paper, we have cloned and expressed the first two genes of this operon from the thermophilic archaeon, Thermoplasma acidophilum. We demonstrate that the protein products form an alpha2beta2 hetero-tetramer possessing the decarboxylase catalytic activity characteristic of the first component enzyme of a branched-chain 2-oxoacid dehydrogenase multienzyme complex. This represents the first report of the catalytic function of these putative archaeal multienzyme complexes.
authors.affiliation: Centre for Extremophile Research, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.
authors.forename: Caroline
authors.initials: C
authors.lastname: Heath
authors.forename: Alex C
authors.initials: AC
authors.lastname: Jeffries
authors.forename: David W
authors.initials: DW
authors.lastname: Hough
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Danson
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002384:Catalysis; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D018387:Codon, Initiator / Q000737:chemistry; D019295:Computational Biology; D003720:Densitometry; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D007658:Ketone Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016366:Open Reading Frames; D009876:Operon; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D013053:Spectrophotometry; D013822:Thermoplasma / Q000201:enzymology*
chemical_list: D019843:Archaeal Proteins; D018387:Codon, Initiator; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D007658:Ketone Oxidoreductases