Fig. 3. Representation of the stalled nascent chain interacting with ribosomal proteins along the exit tunnel.

The isotopically labeled portions are the SecM stalling sequence and the DsbA signal sequence, both depicted as stick models. DsbA is shown in a stretched conformation (left panel) and in a partial α-helical conformation (right panel). Residues for which chemical shifts are indicative for a stretched conformation are color-coded light blue, whereas S¹⁶ and S¹⁸ (adapting an α-helical conformation) are shown in red (right panel). Two of the three proteins that form the constriction point (L⁴ and L²²) and the tRNA (transfer RNA) are shown in blue and are labeled accordingly.