Ubiquitin

Function

Ubiquitin (UBB) is found in almost all cells. It binds to proteins tagging them for destruction in the proteasome. UBB is activated by the UBB-activating enzymes E1, E2 and E3. UBB+1 is a frameshifted mutant of UBB observed in several diseases. A dimer of UBB (DiUBB) is formed by linkage of K48 to the C-terminus of a second UBB molecule. Polyubiquitin (polyUBB) is a chain of ubiquitin bound by peptide bonds. At least 4 UBB molecules are needed to tag a protein for the proteasome^[1]. (3k9p). For details see

• Ubiquitin Structure & Function
  
• Ubiquitin and Ubiquitination
  
• Ubiquitin salt bridge discussion
  
• Ubiquitin chains.

Professors Ciechanover, Hershko and Rose received the Nobel Prize in 2004 for their discovery of the process by which ubiquitin mediates protein proteolysis^[2].

Additional Resources

See also:

• Tumor susceptibility gene 101
• SUMO

Disease

The UBB-proteasome system deregulation has been implicated in the pathogenesis of many neurodegenerative disorders like Alzheimer's disease, Parkinson disease, Huntington disease, Prion-like lethal disorders and in genetic diseases like cystic fibrosis, angelman's syndrome, Liddle syndrome and many cancers^[3].

3D structures of ubiquitin