Ubiquitin and the Proteasome

This animation shows how proteins in the cell are tagged for disposal by ubiquitin and then degraded by the proteasome.

Cells tag misfolded or unneeded proteins with a molecule called ubiquitin. The animation illustrates how ubiquitin is attached to an example protein, ataxin-1, with the help of the ubiquitin carrier enzyme and ubiquitin ligase. Once tagged, ataxin-1 is recognized by a structure called the proteasome, which breaks the protein down into reusable amino acids.

The animation also shows how a mutant form of ataxin-1 cannot be broken down by the proteasome. These mutant proteins accumulate over time and can lead to diseases such as spinocerebellar ataxia type 1 (SCA1).

This animation is a clip from a 2003 Holiday Lecture Series, Learning From Patients: The Science of Medicine. Depending on students’ background, it may be helpful to pause the animation at various points to discuss different parts of the ubiquitin-proteasome system.