title: Identification of a novel dihydrolipoyl dehydrogenase-binding protein in the pyruvate dehydrogenase complex of the anaerobic parasitic nematode, Ascaris suum.
abstract: A novel dihydrolipoyl dehydrogenase-binding protein (E3BP) which lacks an amino-terminal lipoyl domain, p45, has been identified in the pyruvate dehydrogenase complex (PDC) of the adult parasitic nematode, Ascaris suum. Sequence at the amino terminus of p45 exhibited significant similarity with internal E3-binding domains of dihydrolipoyl transacetylase (E2) and E3BP. Dissociation and resolution of a pyruvate dehydrogenase-depleted adult A. suum PDC in guanidine hydrochloride resulted in two E3-depleted E2 core preparations which were either enriched or substantially depleted of p45. Following reconstitution, the p45-enriched E2 core exhibited enhanced E3 binding, whereas, the p45-depleted E2 core exhibited dramatically reduced E3 binding. Reconstitution of either the bovine kidney or A. suum PDCs with the A. suum E3 suggested that the ascarid E3 was more sensitive to NADH inhibition when bound to the bovine kidney core. The expression of p45 was developmentally regulated and p45 was most abundant in anaerobic muscle. In contrast, E3s isolated from anaerobic muscle or aerobic second-stage larvae were identical. These results suggest that during the transition to anaerobic metabolism, E3 remains unchanged, but it appears that a novel E3BP, p45, is expressed which may help to maintain the activity of the PDC in the face of the elevated intramitochondrial NADH/NAD+ ratios associated with anaerobiosis.
authors.affiliation: Department of Biology, University of Toledo, Toledo, Ohio 43606-3390, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Klingbeil
authors.forename: D J
authors.initials: DJ
authors.lastname: Walker
authors.forename: R
authors.initials: R
authors.lastname: Arnette
authors.forename: E
authors.initials: E
authors.lastname: Sidawy
authors.forename: K
authors.initials: K
authors.lastname: Hayton
authors.forename: P R
authors.initials: PR
authors.lastname: Komuniecki
authors.forename: R
authors.initials: R
authors.lastname: Komuniecki
mesh_terms: D000595:Amino Acid Sequence; D000693:Anaerobiosis; D000818:Animals; D017165:Ascaris suum / Q000201:enzymology*; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D015801:Helminth Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D007814:Larva; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D011768:Pyruvate Dehydrogenase Complex / Q000737:chemistry* / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D002352:Carrier Proteins; D015801:Helminth Proteins; D011768:Pyruvate Dehydrogenase Complex; D009243:NAD; D005182:Flavin-Adenine Dinucleotide; D008058:Dihydrolipoamide Dehydrogenase