RNA Mimicry by the Fap7 Adenylate Kinase in Ribosome Biogenesis
Figure 7
Model of Fap7 function in ribosome biogenesis.
(A) Model of the conformational change leading to Rps14 release. The two conformations of the aFap7 NMP domain, the Rps14-CE and Rps14 β4-α2 loop, are represented in red and green. The remaining aFap7 is in surface representation. The seven disordered C-terminal residues of the green conformation are depicted by a dashed line. The extrapolated movement of the three regions suggested to accompany disruption of the Fap7–Rps14 complex is indicated by black arrows (see also Movie S1). (B) During ribosome maturation, Fap7 and Rps14 are bound in the platform domain, which is in a nonnative conformation. After A2 cleavage, Fap7 removes Rps14 from the rRNA. Rps14 is then dissociated from Fap7, probably following ATP hydrolysis, and reincorporated in a near cognate position. This enables a major conformational change to occur that restructures the platform domain and the ITS1, delivering a pre-40S that can undergo the final cleavage at site D. In the absence of Fap7, Rps14 cannot be reincorporated in the ribosome, the rRNA in the platform domain is not remodeled, and cleavage of the D site is not possible, leading to a dead end in the pathway.