Cloning and characterization of EF-Tu and EF-Ts from Pseudomonas aeruginosa.

We have cloned genes encoding elongation factors EF-Tu and EF-Ts from Pseudomonas aeruginosa and expressed and purified the proteins to greater than 95% homogeneity. Sequence analysis indicated that P. aeruginosa EF-Tu and EF-Ts are 84% and 55% identical to E. coli counterparts, respectively. P. aeruginosa EF-Tu was active when assayed in GDP exchange assays. Kinetic parameters for the interaction of EF-Tu with GDP in the absence of EF-Ts were observed to be = 33 μM, = 0.003 s−1, and the specificity constant was  s−1 μM−1. In the presence of EF-Ts, these values were shifted to = 2 μM, = 0.005 s−1, and the specificity constant was  s−1 μM−1. The equilibrium dissociation constants governing the binding of EF-Tu to GDP () were 30–75 nM and to GTP () were 125–200 nM. EF-Ts stimulated the exchange of GDP by EF-Tu 10-fold. P. aeruginosa EF-Tu was active in forming a ternary complex with GTP and aminoacylated tRNA and was functional in poly(U)-dependent binding of Phe-tRNAPhe at the A-site of P. aeruginosa ribosomes. P. aeruginosa EF-Tu was active in poly(U)-programmed polyphenylalanine protein synthesis system composed of all P. aeruginosa components.