Thermodynamic analysis reveals a temperature-dependent change in the catalytic mechanism of bacillus stearothermophilus tyrosyl-tRNA synthetase.

ABSTRACT: Catalysis of tRNA(Tyr) aminoacylation by tyrosyl-tRNA synthetase can be divided into two steps. In the first step, tyrosine is activated by ATP to form the tyrosyl-adenylate intermediate. In the second step, the tyrosyl moiety is transferred to the 3' end of tRNA. To investigate the roles that enthalpic and entropic contributions play in catalysis by Bacillus stearothermophilus tyrosyl-tRNA synthetase (TyrRS), the temperature dependence for the activation of tyrosine and subsequent transfer to tRNA(Tyr) has been determined using single turnover kinetic methods. A van't Hoff plot for binding of ATP to the TyrRS.Tyr complex reveals three distinct regions. Particularly striking is the change occurring at 25 degrees C, where the values of DeltaH(0) and DeltaS(0) go from -144 kJ/mol and -438 J/

SUBMITTER: Sharma G 

PROVIDER: S-EPMC2640972 | biostudies-literature | 2009 Feb

REPOSITORIES: biostudies-literature