Ubiquitin

 
Ubiquitin: A small protein consisting of 76 amino acids. Ubiquitin is virtually ubiquitous. It is found in all types of cells and is one of the most conserved (least changed) proteins known. The amino acid sequence of ubiquitin is identical in all creatures from insects to humans.

In the normal course of cellular events, proteins are inactivated by the attachment of ubiquitin to them (a process called ubiquitination). The ubiquitin acts as a tag by which the protein-transport machinery ferries a protein to the proteosome for degradation. Antagonizing this process are enzymes that remove ubiquitin from proteins.

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