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. Author manuscript; available in PMC: 2020 May 1.
Published in final edited form as: FEBS Lett. 2019 Apr 24;593(10):1009–1019. doi: 10.1002/1873-3468.13383

Fig. 5. The kinetic scheme for the tandem active site model.

Fig. 5.

A. The translation elongation pathway is composed of translocation and dwell steps. PRE and POST denote pre-translocation and post-translocation states of the ribosome complex, respectively. B. The translocation step of panel A is expanded to show the pre-translocation equilibrium in the proximal and distal segments, indicated on the left. The rate of translocation depends on mRNA duplex stability in the proximal segment (affecting the probability of the proximal-bound state), and on mRNA duplex stability in the distal segment (affecting probability of the distal-open state). To be able to translocate at all, the system has to be in the proximal-bound state. To be able to proceed by rapid sliding, it further has to be in the distal-open state. Stick-slip is slow, but can occur from either state of the distal segment. After translocation and during the time controlled by kdwell, the new proximal segment can relax to equilibrium between its three states prior to the next translocation step.