Supplementary Figure 1: Structural overview of the S. cerevisiae 80S ribosome bound with Zuotin and Ssz.

(a-c) Cryo-EM density maps of the empty 80S (a), 80S-Zuotin (b) and 80S-RAC (c) complexes are shown in surface representation, with view direction centered at the PTE (peptide tunnel exit) (a-d). The 60S, 40S, Zuotin, and RAC are colored cyan, yellow, red and orange, respectively. NTD and CTD denote the N- and C-terminal domains of Zuotin. (d) For the 80S-RAC map, densities of Zuotin (red), Ssz (purple) and ES27 (green) were segmented and separately colored. The two maps (b and c) were selected from a large number of similar structures (datasets Zuo1 and RAC6, see Supplementary Table 1), based on their relatively high occupancy of RAC or Zuotin on the ribosome. (e-h) Similar as (a-d), but displayed in a classical front view. (i and j) Overview (i) and close-up view (j) of the interaction of Zuotin with Ssz. The putative densities of Ssz are colored transparent purple, with an atomic model of full-length Ssz (see online methods) docked in its densities (cross-correlation coefficient 0.8329). The map is from the dataset RAC6 (Supplementary Table 1) and filtered to 12 Å. The fitting suggests that Ssz-NTD directly interacts with Zuotin-NTD, which is consistent with previous data that Ssz-CTD does not stably associate with Zuotin³ and is dispensable for its in vivo function⁴.