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Related Concept Videos

Initiation of Translation02:33

Initiation of Translation

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...
Initiation of Translation02:33

Initiation of Translation

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...
Improving Translational Accuracy02:07

Improving Translational Accuracy

Base complementarity between the three base pairs of mRNA codon and the tRNA anticodon is not a failsafe mechanism. Inaccuracies can range from a single mismatch to no correct base pairing at all. The free energy difference between the correct and nearly correct base pairs can be as small as 3 kcal/ mol. With complementarity being the only proofreading step, the estimated error frequency would be one wrong amino acid in every 100 amino acids incorporated. However, error frequencies observed in...
Leaky Scanning02:28

Leaky Scanning

During most eukaryotic translation processes, the small 40S ribosome subunit scans an mRNA from its 5' end until it encounters the first start AUG codon. The large 60S ribosomal subunit then joins the smaller one to initiate protein synthesis. The location of the translation initiation is largely determined by the nucleotides near the start codon as there may be multiple translation initiation sites present on the mRNA.  Marilyn Kozak discovered that the sequence RCCAUGG (where R stands for...
Translation in Prokaryotes01:29

Translation in Prokaryotes

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...
Transcription Initiation01:47

Transcription Initiation

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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Related Experiment Video

Updated: Jun 20, 2026

Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs
10:37

Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs

Published on: May 10, 2018

eIF1 controls multiple steps in start codon recognition during eukaryotic translation initiation.

Jagpreet S Nanda1, Yuen-Nei Cheung, Julie E Takacs

  • 1Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.

Journal of Molecular Biology
|September 16, 2009
PubMed
Summary
This summary is machine-generated.

Eukaryotic translation initiation factor 1 (eIF1) regulates start codon recognition. Mutations at G107 reveal eIF1’s dual role in PIC stability and preventing premature eIF5 binding, crucial for accurate translation initiation.

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Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs
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Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs

Published on: May 10, 2018

Monitoring eIF4F Assembly by Measuring eIF4E-eIF4G Interaction in Live Cells
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Rapid In Vivo Fixation and Isolation of Translational Complexes from Eukaryotic Cells
14:29

Rapid In Vivo Fixation and Isolation of Translational Complexes from Eukaryotic Cells

Published on: December 25, 2021

Area of Science:

  • Molecular Biology
  • Protein-Protein Interactions
  • Gene Expression Regulation

Background:

  • Eukaryotic translation initiation factor 1 (eIF1) is essential for accurate start codon selection during protein synthesis.
  • eIF1 dissociation from the preinitiation complex (PIC) is a key step that triggers downstream events, including phosphate release from eIF2.
  • Mutations weakening eIF1-PIC binding lead to reduced fidelity in start codon recognition (Sui(-) phenotype).

Purpose of the Study:

  • To investigate the function of mutations at the G107 residue of eIF1, which cause Sui(-) phenotypes without altering eIF1 release rates.
  • To elucidate the roles of eIF1 in PIC conformational changes and its interaction with other initiation factors.
  • To understand how eIF1 modulates the fidelity of translation initiation.

Main Methods:

  • Site-directed mutagenesis of the G107 residue in eIF1.
  • Analysis of eIF1 binding and dissociation dynamics within the PIC.
  • Investigating the interplay between eIF1, eIF5, and the PIC.
  • Assessing the impact of mutations on translation initiation fidelity.

Main Results:

  • Mutations at G107 induce Sui(-) phenotypes by mechanisms independent of increased eIF1 release.
  • eIF1 dissociation from the PIC promotes a conformational switch from an open, scanning-competent state to a closed state.
  • eIF5 antagonizes eIF1 binding to the PIC, and this interaction is modulated by the charge at G107.
  • eIF1 prevents eIF5 binding to a critical site in the PIC before AUG recognition.

Conclusions:

  • eIF1 plays multiple, critical roles in ensuring accurate start codon recognition.
  • Beyond gating phosphate release, eIF1 actively stabilizes the PIC in a closed conformation.
  • eIF1's interaction with eIF5 is a key regulatory step in translation initiation, preventing premature activation.
  • Modulating charge at G107 impacts eIF1's interactions and its ability to control PIC states and fidelity.