Catalytic effects of elongation factor Ts on polypeptide synthesis

The kinetic parameters which characterize the interaction between elongation factor Tu (EF-Tu) and elongation factor Ts (EF-Ts) have been determined in a poly(uridylic acid)-primed translation system. The EF-Ts catalyzed release of GDP from EF-Tu was measured independently in a nucleotide exchange assay. We conclude that the rate-limiting step for the EF-Tu cycle in protein synthesis in the absence of EF-Ts is the release of GDP. By adding EF-Ts the time of this step is reduced from 90 s to 30 ms. Half maximal rate is obtained at an EF-Ts concentration of 2.5 x 10 M.