Ubiquitin: new insights into chronic degenerative diseases.

Ubiquitin is a 76-amino-acid protein and is perhaps the most conserved gene product in evolution. It modulates degradation of abnormal or damaged proteins and belongs to the class of heat-shock proteins induced in conditions of cell stress. Recent work shows that ubiquitin is involved in several chronic degenerative diseases characterized by the formation of cellular inclusion bodies. The ubiquitin response to cell injury appears to be cytoprotective and particularly important in diseases of the nervous system.