The Eukaryotic Translation Initiation Factors eIF1 and eIF1A Induce an Open Conformation of the 40S Ribosome
Copyright policy )The Eukaryotic Translation Initiation Factors eIF1 and eIF1A Induce an Open Conformation of the 40S Ribosome
Initiation of translation is the process by which initiator tRNA and the start codon of mRNA are positioned in the ribosomal P site. In eukaryotes, one of the first steps involves the binding of two small factors, eIF1 and eIF1A, to the small (40S) ribosomal subunit. This facilitates tRNA binding, allows scanning of mRNA, and maintains fidelity of start codon recognition. Using cryo-EM, we have obtained 3D reconstructions of 40S bound to both eIF1 and eIF1A, and with each factor alone. These structures reveal that together, eIF1 and eIF1A stabilize a conformational change that opens the mRNA binding channel. Biochemical data reveal that both factors accelerate the rate of ternary complex (eIF2*GTP*Met-tRNA(i)(Met)) binding to 40S but only eIF1A stabilizes this interaction. Our results suggest that eIF1 and eIF1A promote an open, scanning-competent preinitiation complex that closes upon start codon recognition and eIF1 release to stabilize ternary complex binding and clamp down on mRNA.
- Johns Hopkins University School of Medicine United States
- Medical Research Council United Kingdom
- Johns Hopkins Medicine United States
- MRC Laboratory of Molecular Biology United Kingdom
Ribosomal Proteins, Binding Sites, Saccharomyces cerevisiae Proteins, Models, Genetic, Cryoelectron Microscopy, Eukaryotic Initiation Factor-1, Molecular Conformation, Cell Biology, Saccharomyces cerevisiae, Structure-Activity Relationship, RNA, Ribosomal, Protein Biosynthesis, RNA, Messenger, Molecular Biology, Ribosomes, Protein Binding
Ribosomal Proteins, Binding Sites, Saccharomyces cerevisiae Proteins, Models, Genetic, Cryoelectron Microscopy, Eukaryotic Initiation Factor-1, Molecular Conformation, Cell Biology, Saccharomyces cerevisiae, Structure-Activity Relationship, RNA, Ribosomal, Protein Biosynthesis, RNA, Messenger, Molecular Biology, Ribosomes, Protein Binding
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