Fig. 5: Structural remodeling of RAC when engaging with the nascent chain.

a–c Magnified views at the PTE region of State C1-C3 from the RNC-RAC datasets (Map 3.1, Map 3.5 and Map 3.3 in Supplementary Fig. 9). The ribosome is colored gray, and Zuo1 ND, JD, ZHD and Ssz1 are shown in green, blue, orange and pink, respectively. The location of the HPD motif is labelled by a cyan box, and the PTE, uL24, H7-loop and ES24 is labeled. d Magnified view at the PTE region of the structure from the RNC-RAC-Ssb1 dataset (Map 2.2 in Supplementary Fig. 6). e–h Structural transition from State C1 (a) to C2 (b). Nearly 180°-rotation of Ssz1 roughly round the HPD motif (Zuo1 JD as reference for alignment) (g) and rotation of Zuo1-NTD away from the PTE (h). Ssz1 NBD and SBD are colored lavender and pink, respectively. Models of RAC in State C1 before the transition in g–h are colored gray. The ribosome-interacting region in Ssz1 NBD-IIB is labelled by dash-line box in red (C1) or black (C2). H7-loop of the 25S rRNA is also shown as a landmark for comparison, with the nucleotide G85 in stick model. Upon the transition, the distance between G85 and the H128 of the HPD motif increases from 67 to 83 Å.