title: Modulation of functionally significant conformational equilibria in adenylate kinase by high concentrations of trimethylamine oxide attributed to volume exclusion.
abstract: The effect of an inert small molecule osmolyte, trimethyl amine N-oxide (TMAO), upon the conformational equilibria of Escherichia coli adenylate kinase was studied using time-resolved FRET. The relative populations of open and closed clefts between the LID and the CORE domains were measured as functions of the concentrations of the substrate ATP over the concentration range 0-18 mM and TMAO over the concentration range 0-4 M. A model was constructed according to which the enzyme exists in equilibrium among four conformational states, corresponding to combinations of open and closed conformations of the LID-CORE and AMP-CORE clefts. ATP is assumed to bind only to those conformations with the closed LID-CORE cleft, and TMAO is assumed to be differentially excluded as a hard spherical particle from each of the four conformations in accordance with calculations based upon x-ray crystallographic structures. This model was found to describe quantitatively the dependence of the fraction of the closed LID-CORE cleft upon the concentrations of both ATP and TMAO over the entire range of concentrations with just five undetermined parameters.
authors.affiliation: The Goodman Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel.
authors.forename: Sureshbabu
authors.initials: S
authors.lastname: Nagarajan
authors.forename: Dan
authors.initials: D
authors.lastname: Amir
authors.forename: Asaf
authors.initials: A
authors.lastname: Grupi
authors.forename: David P
authors.initials: DP
authors.lastname: Goldenberg
authors.forename: Allen P
authors.initials: AP
authors.lastname: Minton
authors.forename: Elisha
authors.initials: E
authors.lastname: Haas
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000263:Adenylate Kinase / Q000737:chemistry*; D000596:Amino Acids / Q000378:metabolism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology*; D031541:Fluorescence Resonance Energy Transfer; D007700:Kinetics; D008024:Ligands; D046911:Macromolecular Substances / Q000378:metabolism; D008744:Methylamines / Q000737:chemistry / Q000494:pharmacology*; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013997:Time Factors
chemical_list: D000596:Amino Acids; D008024:Ligands; D046911:Macromolecular Substances; D008744:Methylamines; D000255:Adenosine Triphosphate; D000263:Adenylate Kinase; C005855:trimethyloxamine