ABSTRACT
Ubiquitin A small protein present in all eucaryotic cells (i.e., it is ubiquitous), which plays an important role in “tagging” other protein molecules (e.g., old ones that are degraded, misfolded, or no longer needed) so that they are destined (marked) for destruction (via proteolytic cleavage). Such proteins are then broken down in cell’s proteasomes and their constituents recycled because they are damaged or no longer needed by the body. The ubiquitin molecules are then available for reuse.
