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.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Amino Acid Substitution
-
Binding Sites
-
Catalysis
-
Crystallography, X-Ray
-
Dihydrolipoyllysine-Residue Acetyltransferase
-
Geobacillus stearothermophilus / enzymology*
-
Hydrogen-Ion Concentration
-
Hydrophobic and Hydrophilic Interactions
-
Kinetics
-
Models, Molecular
-
Mutation
-
Phosphorylation
-
Protein Conformation
-
Protein Folding
-
Protein Structure, Quaternary
-
Protein Structure, Tertiary
-
Protein Subunits / chemistry
-
Protein Subunits / metabolism
-
Protons
-
Pyruvate Dehydrogenase (Lipoamide) / chemistry*
-
Pyruvate Dehydrogenase (Lipoamide) / genetics
-
Pyruvate Dehydrogenase (Lipoamide) / metabolism*
-
Pyruvate Dehydrogenase Complex / chemistry*
-
Pyruvate Dehydrogenase Complex / metabolism*
-
Pyruvic Acid / metabolism
-
Thiamine Pyrophosphate / metabolism*
Substances
-
Protein Subunits
-
Protons
-
Pyruvate Dehydrogenase Complex
-
Pyruvic Acid
-
Pyruvate Dehydrogenase (Lipoamide)
-
Dihydrolipoyllysine-Residue Acetyltransferase
-
Thiamine Pyrophosphate