Discovery of signal peptides
The 1999 Nobel Prize in Physiology or Medicine was awarded to Günter Blobel for the discovery that proteins have intrinsic signals that govern their transport and localization in the cell. Blobel first suggested this as a hypothesis in 1971 and then went on to develop experiments to demonstrate and characterise these signals.
To study these signals, Blobel needed to reduce the complexity of the processes in the cell and stripped it down to the barest parts. By taking different parts from dog, rabbit, rat and mouse cells, he was able to demonstrate cell-free protein synthesis, in which the protein-making machinery of the cell can be examined in vitro.
These experiments showed that proteins have certain tags attached to them that determines where they are destined to be placed within the cell. These signal tags are found throughout eukaryotic life and are a fundamental aspect of cellular behaviour.