Recruitment of elongation factor EF-G to the ribosome requires interaction between ribosomal proteins L12 and L11. New analyses identify a proline switch in L11, with the cis configuration allowing direct interaction between L11 and L12. EF-G has peptidyl-prolyl cis-trans isomerase activity driving the cis-trans isomerization of the proline switch, which might be a universal mechanism for efficient turnover of translational GTPases.
