Figure 4.

Visualization by Cryo-EM of the ADR1a Domain in a Stalled Ribosome-ADR1a-SecM (Ms-Sup1; L = 25) Complex

(A) Schematic of the construct used for in vitro translation (top) and cryo-EM reconstructions of stalled E. coli ribosome-SecM-ADR1a complexes (left). The 30S subunit is depicted in yellow, the 50S subunit in gray, and the peptidyl-tRNA with the nascent polypeptide chain in green. Additionally, a cross-section through the cryo-EM density is shown in which the density for the nascent chain and the ADR1a domain (PDB: 2ADR) are depicted in green and red, respectively. A close-up of the tunnel and a schematic view are shown with the structure of the ADR1a domain fitted as rigid body depicted in red.

(B) Isolated density for the ADR1a domain (red) shown at different contour levels (top) compared with corresponding densities calculated from the NMR-derived molecular model of ADR1a (middle). Isolated cryo-EM density is shown transparent with the docked model (red) and the coordinated Zn²⁺ ion in yellow (bottom).

See also Figure S4.