FIGURE 2.

Energetic profile of P-site codon:anticodon complexes. P-site tRNA dissociated from mRNA is considered as an activation complex for P-site tRNA repositioning. Transition from a tRNA: mRNA complex with the codon in the initial frame to where the codon is in an alternative frame, can be achieved in two ways: (1) by increasing the rate constant of the forward reaction (higher energy of the initial complex); and (2) by decreasing the rate constant of the reverse reaction (lower energy of the new complex).