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Related Concept Videos

Initiation of Translation02:33

Initiation of Translation

37.4K
Initiating translation is complex because it involves multiple molecules. Initiator tRNA, ribosomal subunits, and eukaryotic initiation factors (eIFs) are all required to assemble on the initiation codon of mRNA. This process consists of several steps that are mediated by different eIFs.
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
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Initiation of Translation02:33

Initiation of Translation

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Translation in Prokaryotes01:29

Translation in Prokaryotes

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Prokaryote translation is a complex, highly coordinated process that converts genetic information from mRNA into functional proteins. It involves three stages: initiation, elongation, and termination, each facilitated by specific molecular components.Initiation of TranslationThe process begins with the assembly of the ribosomal subunits and initiation factors on the mRNA. In bacteria, the 30S ribosomal subunit recognizes the Shine-Dalgarno sequence in the mRNA, a conserved region upstream of...
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Termination of Translation01:44

Termination of Translation

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The large ribosomal subunit has several important structures essential to translation. These include the peptidyl transferase center (PTC) - which is the site where the peptide bond is formed - and a large, internal, water-filled tube through which the nascent polypeptide moves. This latter structure is called the Peptide Exit Tunnel, and it begins at the PTC and spans the body of the large ribosomal subunit. During translation, as the nascent polypeptide chain is synthesized, it passes through...
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Transcription Initiation01:47

Transcription Initiation

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Initiation is the first step of transcription in eukaryotes. Prokaryotic RNA Polymerase (RNAP) can bind to the template DNA and start transcribing. On the other hand, transcription in eukaryotes requires additional proteins, called transcription factors, to first bind to the promoter region in the DNA template. This binding helps recruit the specific RNAP that can assemble on the DNA and start transcription.
The promoters and enhancers and their accessory proteins allow tight regulation of...
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Cotranslational Protein Translocation01:20

Cotranslational Protein Translocation

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Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
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Related Experiment Video

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Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs
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Structure of a human 48S translational initiation complex.

Jailson Brito Querido1, Masaaki Sokabe2, Sebastian Kraatz1

  • 1MRC Laboratory of Molecular Biology, Cambridge, UK.

Science (New York, N.Y.)
|September 5, 2020
PubMed
Summary

Researchers visualized the 48S initiation complex, revealing how the cap-binding complex (eIF4F) recruits mRNA. This structure provides insights into mRNA scanning and unwinding during the early stages of translation.

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Area of Science:

  • Molecular Biology
  • Structural Biology
  • Biochemistry

Background:

  • Translation initiation is a critical step in protein synthesis.
  • The 43S preinitiation complex is recruited by the eIF4F cap-binding complex to mRNA.
  • This interaction forms the 48S initiation complex, which then scans for the start codon.

Purpose of the Study:

  • To elucidate the structural mechanisms of translation initiation complex assembly.
  • To understand the interaction between eIF4F and the 43S complex during mRNA recruitment.
  • To investigate the process of start codon scanning and mRNA unwinding.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) was employed.
  • A reconstituted human 48S initiation complex was analyzed.
  • High-resolution structural determination of the complex.

Main Results:

  • The cryo-EM structure of the human 48S initiation complex was determined.
  • Insights into the early assembly events of the translation initiation complex were gained.
  • The interaction of eIF4F with eIF3 subunits near the mRNA exit channel was visualized.
  • The positioning of eIF4F supports a slotting model for mRNA recruitment.

Conclusions:

  • The structure provides a detailed view of mRNA recruitment and scanning.
  • The findings suggest that mRNA is unwound by being pulled through the 40S ribosomal subunit during scanning.
  • This work advances our understanding of the fundamental process of eukaryotic translation initiation.