Figure 4: Imp3 is not the placeholder factor for the assembly of S9 r-protein. (A) Position of Imp3 (red) and S9 (medium blue) in the 90S pre-ribosomal particle, also known as the SSU processome (PDB ID: 5TZS; [93]). (B) Position of S9 r-protein (royal blue) in the mature 40S r-subunit (PDB ID: 3U5B, 3U5C; [44]). Mature 40S r-subunit is seen from the A-site view, and the 90S pre-ribosomal particles has been consequently oriented from a similar position regarding the nascent 40S r-subunit. The positions of the U3 snoRNP (yellow) and that of the S4 r-protein (cyan) have been highlighted. The 5′ domain of 18S rRNA has been coloured in dark grey, the central domain in medium grey, and the rest of 18S rRNAs in pale blue; r-proteins and/or factors have been coloured in light cornflower blue.

44. Ben-Shem A, Garreau de Loubresse N, Melnikov S, Jenner L, Yusupova G, Yusupov M (2011). The structure of the eukaryotic ribosome at 3.0 Å resolution. Science 334(6062): 1524-1529. https://doi.org/10.1126/science.1212642

93. Chaker-Margot M, Barandun J, Hunziker M, Klinge S (2016). Architecture of the yeast small subunit processome. Science 355(6321). https://doi.org/10.1126/science.aal1880