Role of the conserved aspartate and phenylalanine residues in prokaryotic and mitochondrial elongation factor Ts in guanine nucleotide exchange.

The guanine nucleotide exchange reaction catalyzed by elongation factor Ts is proposed to arise from the intrusion of the side chains of D80 and F81 near the Mg2+ binding site in EF-Tu. D80A and F81A mutants of E. coli EF-Ts were 2-3-fold less active in promoting GDP exchange with E. coli EF-Tu while the D80AF81A mutant was nearly 10-fold less active. The D84 and F85 mutants of EF-Tsmt were 5-10-fold less active in stimulating the activity of EF-Tumt. The double mutation completely abolished the activity of EF-Tsmt.