title: Dissociation of the octameric enolase from S. pyogenes--one interface stabilizes another.
abstract: Most enolases are homodimers. There are a few that are octamers, with the eight subunits arranged as a tetramer of dimers. These dimers have the same basic fold and same subunit interactions as are found in the dimeric enolases. The dissociation of the octameric enolase from S. pyogenes was examined, using NaClO(4), a weak chaotrope, to perturb the quaternary structure. Dissociation was monitored by sedimentation velocity. NaClO(4) dissociated the octamer into inactive monomers. There was no indication that dissociation of the octamer into monomers proceeded via formation of significant amounts of dimer or any other intermediate species. Two mutations at the dimer-dimer interface, F137L and E363G, were introduced in order to destabilize the octameric structure. The double mutant was more easily dissociated than was the wild type. Dissociation could also be produced by other salts, including tetramethylammonium chloride (TMACl) or by increasing pH. In all cases, no significant amounts of dimers or other intermediates were formed. Weakening one interface in this protein weakened the other interface as well. Although enolases from most organisms are dimers, the dimeric form of the S. pyogenes enzyme appears to be unstable.
authors.affiliation: Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec, Canada.
authors.forename: Farhad
authors.initials: F
authors.lastname: Karbassi
authors.forename: Veronica
authors.initials: V
authors.lastname: Quiros
authors.forename: Vijay
authors.initials: V
authors.lastname: Pancholi
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Kornblatt
mesh_terms: D002942:Circular Dichroism; D019281:Dimerization; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D010751:Phosphopyruvate Hydratase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D013297:Streptococcus pyogenes / Q000201:enzymology*; D014461:Ultracentrifugation
chemical_list: D010751:Phosphopyruvate Hydratase