Structural basis of GTPase-mediated mitochondrial ribosome biogenesis and recycling

Abstract Ribosome biogenesis requires auxiliary factors to promote folding and assembly of ribosomal proteins RNA. Particularly, maturation the peptidyl transferase center (PTC) is mediated by conserved GTPases, but molecular basis poorly understood. Here, we define mechanism GTPase-driven human mitochondrial large subunit (mtLSU) using endogenous complex purification, in vitro reconstitution cryo-EM. Structures transient native mtLSU intermediates that accumulate GTPBP6-deficient cells reveal how GTPBP5, MTERF4 NSUN4 facilitate PTC folding. Addition recombinant GTPBP6 reconstitutes late shows triggers a switch progression near-mature state. Additionally, cryo-EM analysis GTPBP6-treated mature ribosomes reveals structural for dual-role ribosome recycling. Together, these results provide framework understanding step-wise as critical quality control checkpoint.