Kiss of Death Gets Nobel Prize

Medical Authors and Editors: Barbara K. Hecht, Ph.D. and Frederick Hecht, M.D.

October 7, 2004 -- The 2004 Nobel Prize in Chemistry has been awarded to three scientists who found the "kiss of death" for proteins. Aaron Ciechanover and Avram Hershko of the Technion Israel Institute of Technology in Haifa, Israel and Irwin Rose of the University of California, Irvine shared this year's prize "for the discovery of ubiquitin-mediated protein degradation."

The Kiss of Death

The "kiss of death" for proteins is called ubiquitin. It is itself a protein, a tiny one consisting of only 76 amino acids. It acts as the "kiss of death" for other proteins.

In the normal course of events, proteins need to be broken down and their parts recycled. This is done, it turns out, by tagging proteins with ubiquitin, a process called ubiquination.

Ubiquitin is the signal to the cell's transport machinery to ferry a protein to the proteasome, a barrel-shaped chamber floating in the cell cytoplasm. Proteasomes then slice the protein into bits that are recycled into new proteins.

Antagonizing this process are enzymes that remove ubiquitin from proteins and prevent them being degraded.