28. Intracellular proteolysis

Last updated on November 19, 2018 at 17:16


  • All cells need to degrade intracellular proteins constantly. Protein degradation is involved also involved in regulation.
  • In prokaryotes, degradation is done by Lon, an ATP dependent protease
  • Eukaryotes target proteins that should be degraded with ubiquitin, and the proteasome degrades these proteins.
  • The ubiquitin-protease system is important in gene transcription, cell cycle regulation and apoptosis.

Thankfully, this is a small topic

How E1, E2 and E3 tag proteins with ubiquitin.

The cell targets proteins that should be degraded by “tagging” them with ubiquitin, a special protein. This tagging is catalysed by three proteins: E1, E2 and E3. All three are needed to tag the target protein with ubiquitin. Proteins can be tagged with many ubiquitin molecules, to accelerate their degradation.

The ubiquitinated proteins are degraded by a large protein complex known as the 26S proteasome.

Previous page:
27. Protein targeting and vesicular transport of proteins

Next page:
29. Regulation of gene expression

Leave a Reply

Only the "Comment" field must be filled in. It is not compulsory to fill out your name; you can remain anonymous. Do not fill out e-mail or website; if you do, your comment will not be published.