title: Temperature dependence of internal friction in enzyme reactions.
abstract: Our aim was to elucidate the physical background of internal friction of enzyme reactions by investigating the temperature dependence of internal viscosity. By rapid transient kinetic methods, we directly measured the rate constant of trypsin 4 activation, which is an interdomain conformational rearrangement, as a function of temperature and solvent viscosity. We found that the apparent internal viscosity shows an Arrhenius-like temperature dependence, which can be characterized by the activation energy of internal friction. Glycine and alanine mutations were introduced at a single position of the hinge of the interdomain region to evaluate how the flexibility of the hinge affects internal friction. We found that the apparent activation energies of the conformational change and the internal friction are interconvertible parameters depending on the protein flexibility. The more flexible a protein was, the greater proportion of the total activation energy of the reaction was observed as the apparent activation energy of internal friction. Based on the coupling of the internal and external movements of the protein during its conformational change, we constructed a model that quantitatively relates activation energy, internal friction, and protein flexibility.
authors.affiliation: Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/C, Budapest H-1117, Hungary.
authors.forename: Anna Á
authors.initials: AÁ
authors.lastname: Rauscher
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Simon
authors.forename: Gergely J
authors.initials: GJ
authors.lastname: Szöllosi
authors.forename: László
authors.initials: L
authors.lastname: Gráf
authors.forename: Imre
authors.initials: I
authors.lastname: Derényi
authors.forename: Andras
authors.initials: A
authors.lastname: Malnasi-Csizmadia
mesh_terms: D019943:Amino Acid Substitution; D004548:Elasticity; D004789:Enzyme Activation; D004798:Enzymes / Q000737:chemistry* / Q000378:metabolism*; D017276:Friction; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008954:Models, Biological; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D044367:Phase Transition; D011487:Protein Conformation; D013696:Temperature; D013816:Thermodynamics; D014357:Trypsin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014783:Viscosity
chemical_list: D004798:Enzymes; D050505:Mutant Proteins; C040749:PRSS3 protein, human; D014357:Trypsin