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. Author manuscript; available in PMC: 2014 May 1.
Published in final edited form as: Trends Cell Biol. 2013 Feb 1;23(5):242–250. doi: 10.1016/j.tcb.2013.01.004

Figure 2.

Figure 2

A translation-like cycle during 40S ribosome maturation. Adapted from [29]. The cycle starts with the dissociation of Ltv1 from the intermediate visualized by cryo-EM (I). The translation factor eIF5B, a GTPase, then promotes joining of 60S subunits, analogous to its function during translation, to give an 80S-like complex, lacking both mRNA and tRNA (III). Rio2 dissociates with or soon after 60S joining to give a stable 80S-like complex (IV), which accumulates in the absence of the ATPase Fap7. Dissociation of Tsr1 (V) allows for Nob1-dependent rRNA maturation (VI) and access of Dom34 and Rli1 to separate 80S-like ribosomes (VII). Exchange of S26 for Pno1 appears to be the final step in maturation. The small and large ribosomal subunits are shown in light and dark grey, respectively. Stably bound assembly factors are shown in yellow. ATP or GTP-hydrolyzing transiently bound factors are shown in magenta, other transiently bound factors are shown in green and mRNA is shown as a blue band.