Figure 5.

Competition between GTPase deficient and wild type T₃ for native and m⁶A modified A-site codon. Fraction of fMet-Glu formed (y-axis) at different reaction times (x-axis, log₁₀ display) in experiments where free T₃ with wild type EF-Tu competes with GTPase deficient H84A-mutated EF-Tu for ribosomes with GAA (closed squares) and Gm⁶AA (open circles) codons. Both types of ternary complex are rapidly added to ribosomal complex RC₂ (Figure 1) leading to rapid peptide bond formation upon initial native T₃ binding and slow peptide bond formation upon initial GTPase deficient T₃ binding and its eventual exchange for native T₃. Note that peptide bond formation is much slower at Gm⁶AA than GAA codons due to m⁶A-dependent reduction of the rate constant for binding of T₃ to A site (see main text).