Mechanism of mitoribosomal small subunit biogenesis and preinitiation
Copyright policy )Mechanism of mitoribosomal small subunit biogenesis and preinitiation
AbstractMitoribosomes are essential for the synthesis and maintenance of bioenergetic proteins. Here we use cryo-electron microscopy to determine a series of the small mitoribosomal subunit (SSU) intermediates in complex with auxiliary factors, revealing a sequential assembly mechanism. The methyltransferase TFB1M binds to partially unfolded rRNA h45 that is promoted by RBFA, while the mRNA channel is blocked. This enables binding of METTL15 that promotes further rRNA maturation and a large conformational change of RBFA. The new conformation allows initiation factor mtIF3 to already occupy the subunit interface during the assembly. Finally, the mitochondria-specific ribosomal protein mS37 (ref. 1) outcompetes RBFA to complete the assembly with the SSU–mS37–mtIF3 complex2 that proceeds towards mtIF2 binding and translation initiation. Our results explain how the action of step-specific factors modulate the dynamic assembly of the SSU, and adaptation of a unique protein, mS37, links the assembly to initiation to establish the catalytic human mitoribosome.
- Max Planck Society Germany
- Science for Life Laboratory Sweden
- Stockholm University Sweden
- Karolinska Institute Sweden
- Skolkovo Institute of Science and Technology Russian Federation
Ribosomal Proteins, Cryoelectron Microscopy, RNA-Binding Proteins, Article, Mitochondria, Ribosome Subunits, Small, DNA-Binding Proteins, Mitochondrial Proteins, Mitochondrial Ribosomes, RNA, Ribosomal, Humans, Eukaryotic Initiation Factors, Transcription Factors
Ribosomal Proteins, Cryoelectron Microscopy, RNA-Binding Proteins, Article, Mitochondria, Ribosome Subunits, Small, DNA-Binding Proteins, Mitochondrial Proteins, Mitochondrial Ribosomes, RNA, Ribosomal, Humans, Eukaryotic Initiation Factors, Transcription Factors
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