Aaron Ciechanover, Avram Hershko and Irwin Rose have brought us to realise that the cell functions as a highly-efficient checking station where proteins are built up and broken down at a furious rate. The degradation is not indiscriminate but takes place through a process that is controlled in detail so that the proteins to be broken down at any given moment are given a molecular label, a ‘kiss of death', to be dramatic. The labelled proteins are then fed into the cells' "waste disposers", the so called proteasomes, where they are chopped into small pieces and destroyed.
Picture the poor cells, accompanied by the mysterious, dark-clad, perhaps hooded Ubiquitin (he's everywhere!) down a long hallway to meet their fates. No words are exchanged, just a tap on the shoulder, a "kiss" of acknowledgement. The proteasomes stormtroopers await.
Dramatic indeed! There's a movie in this somewhere.