How TnaC turns the bacterial ribosome into a tryptophan sensor

van der Stel, A.X., Gordon, E.R., Sengupta, A., Martínez, A.K., Klepacki, D., Perry, T.N., Herrero Del Valle, A., Vázquez-Laslop, N., Sachs, M.S., Cruz-Vera, L.R., Innis, C.A. (2021). Structural basis for the tryptophan sensitivity of TnaC-mediated ribosome stalling. Nat Commun 12, 5340.

PDB entries : 7O19, 7O1A, 7O1C

EMDB entries : EMD-12693, EMD-12694, EMD-12695

In this work, we reveal the mechanism by which the ribosome-arresting peptide TnaC captures a single L-Tryptophan molecule to trigger the production of indole. Moreover, analysis of a TnaC variant (R23F) that stalls ribosomes at much lower L-Tryptophan concentrations than wild-type TnaC suggests that the sensitivity of the system is the result of a fine balance between the kinetics of ligand binding and peptide release by RF2.