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Phosphorylation01:02

Phosphorylation

The addition or removal of phosphate groups from proteins is the most common chemical modification that regulates cellular processes. These modifications can affect the structure, activity, stability, and localization of proteins within cells as well as their interactions with other proteins.
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
Protein Kinases and Phosphatases02:54

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
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...
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...
Protein Kinases and Phosphatases02:54

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
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...

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Related Experiment Video

Updated: Jul 10, 2026

Xenopus laevis as a Model to Identify Translation Impairment
10:24

Xenopus laevis as a Model to Identify Translation Impairment

Published on: September 27, 2015

Protamine kinase phosphorylates eukaryotic protein synthesis initiation factor 4E.

G D Amick1, Z Damuni

  • 1Department of Biological Sciences, University of South Carolina, Columbia 29208.

Biochemical and Biophysical Research Communications
|March 16, 1992
PubMed
Summary

Bovine kidney protamine kinase phosphorylates eukaryotic initiation factor 4E (eIF-4E), suggesting its role in insulin signaling. Other kinases showed minimal activity with eIF-4E.

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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
  • Biochemistry
  • Cell Signaling

Background:

  • Eukaryotic protein synthesis initiation factor 4E (eIF-4E) is a key regulator of cap-dependent translation.
  • Phosphorylation of eIF-4E plays a crucial role in controlling protein synthesis and cell growth.
  • Insulin signaling is known to influence eIF-4E phosphorylation, but the specific kinases involved are not fully elucidated.

Purpose of the Study:

  • To investigate the activity of various protein kinases towards purified eukaryotic initiation factor 4E (eIF-4E).
  • To identify potential kinases responsible for the insulin-stimulated phosphorylation of eIF-4E.

Main Methods:

  • Purified preparations of eukaryotic initiation factor 4E (eIF-4E) were incubated with purified protamine kinase from bovine kidney cytosol.
  • The phosphorylation activity of protamine kinase, mitogen-activated protein kinase, casein kinase II, and an autophosphorylation-activated protein kinase on eIF-4E was assessed.

Main Results:

  • Protamine kinase incorporated up to 1 mol of phosphoryl groups per mol of eIF-4E.
  • Mitogen-activated protein kinase, casein kinase II, and the autophosphorylation-activated protein kinase showed little to no activity with eIF-4E.

Conclusions:

  • Protamine kinase is a significant phosphorylating agent for eIF-4E.
  • These findings suggest that protamine kinase may be the kinase responsible for insulin-stimulated eIF-4E phosphorylation.