Extended Data Fig. 3: Features of the Rho-2TMD map and model.

a, b, Two views from the plane of the membrane of the Rho-2TMD reference map, low-pass filtered to 7 Å resolution, fitted with the model. The approximate position of the membrane is indicated. The detergent micelle and ribosome are omitted for clarity. c, View from the ER lumen of the low-pass filtered Rho-2TMD reference map fitted with the model. The clipping plane is within the membrane close to the ER lumen. The detergent micelle and ribosome are omitted for clarity, with the position of the ribosome tunnel exit indicated. d, Overview of the low-pass filtered reference map in the context of the detergent micelle and ribosome. The map is shown at two contour levels. The blue line shows a low contour level at which lumenal density and the complete micelle is visible. The opaque density is shown at a higher contour level to visualise the translocon, coloured as in panels a-c. The ribosome and micelle are in transparent grey. e, The PAT sub-classified map (submap 2 in Extended Data Fig. 2) filtered by local resolution viewed from the ribosome to illustrate that the regions closest to (and stabilised by) the ribosome are particularly well resolved. The position of the nascent chain density and the mouth of the ribosome exit tunnel are indicated. f, Space-filling depictions of the Rho-2TMD model illustrating how the C-terminal region of CCDC47 enters the mouth of the ribosome exit tunnel, abuts the nascent chain, and narrows the exit tunnel dimensions. The top shows overviews before and after clipping, with dashed boxes indicating the regions shown at higher magnification below.