title: A molecular switch and proton wire synchronize the active sites in thiamine enzymes.
abstract: Thiamine diphosphate (ThDP) is used as a cofactor in many key metabolic enzymes. We present evidence that the ThDPs in the two active sites of the E1 (EC 1.2.4.1) component of the pyruvate dehydrogenase complex communicate over a distance of 20 angstroms by reversibly shuttling a proton through an acidic tunnel in the protein. This "proton wire" permits the co-factors to serve reciprocally as general acid/base in catalysis and to switch the conformation of crucial active-site peptide loops. This synchronizes the progression of chemical events and can account for the oligomeric organization, conformational asymmetry, and "ping-pong" kinetic properties of E1 and other thiamine-dependent enzymes.
authors.affiliation: Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, UK.
authors.forename: René A W
authors.initials: RA
authors.lastname: Frank
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Titman
authors.forename: J Venkatesh
authors.initials: JV
authors.lastname: Pratap
authors.forename: Ben F
authors.initials: BF
authors.lastname: Luisi
authors.forename: Richard N
authors.initials: RN
authors.lastname: Perham
mesh_terms: D019943:Amino Acid Substitution; D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D051047:Dihydrolipoyllysine-Residue Acetyltransferase; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D010766:Phosphorylation; D011487:Protein Conformation; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011522:Protons; D030481:Pyruvate Dehydrogenase (Lipoamide) / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011768:Pyruvate Dehydrogenase Complex / Q000737:chemistry* / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D013835:Thiamine Pyrophosphate / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D011522:Protons; D011768:Pyruvate Dehydrogenase Complex; D019289:Pyruvic Acid; D030481:Pyruvate Dehydrogenase (Lipoamide); D051047:Dihydrolipoyllysine-Residue Acetyltransferase; D013835:Thiamine Pyrophosphate