title: Substrate-dependent switching of the allosteric binding mechanism of a dimeric enzyme.
abstract: Enzyme activity is commonly controlled by allostery, where ligand binding at one site alters the activities of distant sites. Classical explanations for multisubunit proteins involve conformational transitions that are fundamentally deterministic. For example, in the Monod-Wyman-Changeaux (MWC) paradigm, conformational transitions occur simultaneously in all subunits. In the Koshland-Nemethy-Filmer (KNF) paradigm, conformational transitions only occur in ligand-bound subunits. In contrast, recent models predict conformational changes that are governed by probabilities rather than absolute rules. To better understand allostery at the molecular level, we applied a recently developed spectroscopic and calorimetric method to the interactions of a dimeric enzyme with two different ligands. We found that conformational transitions appear MWC-like for a ligand that binds at the dimer interface and KNF-like for a distal ligand. These results provide strong experimental support for probabilistic allosteric theory predictions that an enzyme can exhibit a mixture of MWC and KNF character, with the balance partly governed by subunit interface energies.
authors.affiliation: Department of Chemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Lee
authors.initials: L
authors.lastname: Freiburger
authors.affiliation: Department of Chemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Teresa
authors.initials: T
authors.lastname: Miletti
authors.affiliation: Department of Chemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Siqi
authors.initials: S
authors.lastname: Zhu
authors.affiliation: Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Oliver
authors.initials: O
authors.lastname: Baettig
authors.affiliation: Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Albert
authors.initials: A
authors.lastname: Berghuis
authors.affiliation: Department of Chemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Karine
authors.initials: K
authors.lastname: Auclair
authors.affiliation: Department of Chemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Anthony
authors.initials: A
authors.lastname: Mittermaier
mesh_terms: D000105:Acetyl Coenzyme A / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000123:Acetyltransferases / Q000737:chemistry* / Q000378:metabolism*; D000494:Allosteric Regulation / Q000187:drug effects; D001665:Binding Sites / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D008024:Ligands; D008958:Models, Molecular; D010303:Paromomycin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D055503:Protein Multimerization / Q000187:drug effects; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D058767:Protein Unfolding; D013329:Structure-Activity Relationship; D013379:Substrate Specificity / Q000187:drug effects; D013816:Thermodynamics
chemical_list: D008024:Ligands; D021122:Protein Subunits; D010303:Paromomycin; D000105:Acetyl Coenzyme A; D000123:Acetyltransferases; C019681:aminoglycoside acetyltransferase