Complete kinetic mechanism for recycling of the bacterial ribosome.

Anneli Borg, Michael Pavlov, Måns Ehrenberg

RNA (New York, N.Y.) 2016 Jan

filter terms:

How EF-G and RRF act together to split a post-termination ribosomal complex into its subunits has remained obscure. Here, using stopped-flow experiments with Rayleigh light scattering detection and quench-flow experiments with radio-detection of GTP hydrolysis, we have clarified the kinetic mechanism of ribosome recycling and obtained precise estimates of its kinetic parameters. Ribosome splitting requires that EF-G binds to an already RRF-containing ribosome. EF-G binding to RRF-free ribosomes induces futile rounds of GTP hydrolysis and inhibits ribosome splitting, implying that while RRF is purely an activator of recycling, EF-G acts as both activator and competitive inhibitor of RRF in recycling of the post-termination ribosome. The ribosome splitting rate and the number of GTPs consumed per splitting event depend strongly on the free concentrations of EF-G and RRF. The maximal recycling rate, here estimated as 25 sec(-1), is approached at very high concentrations of EF-G and RRF with RRF in high excess over EF-G. The present in vitro results, suggesting an in vivo ribosome recycling rate of ∼5 sec(-1), are discussed in the perspective of rapidly growing bacterial cells. © 2015 Borg et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

Citation

Anneli Borg, Michael Pavlov, Måns Ehrenberg. Complete kinetic mechanism for recycling of the bacterial ribosome. RNA (New York, N.Y.). 2016 Jan;22(1):10-21