[The 1994 Nobel Prize: discovery and significance of G-proteins]

Exactly how a cell responds to a hormone or transmitter substance depends on at least three factors: which type of receptors the cell has, which G-proteins are present and which amplifying system exists in precisely that cell. This means that the number of possible signalling pathways becomes extremely great. Here lies the most important aspect of the discoveries that have been rewarded with this year's Nobel prize. The translation of a message from an extracellular signal to an altered cellular function demands reoperation between a cascade of different proteins. One cell has one certain structure, another contains quite different components. In this manner, a limited number of signals and signal-transmitting molecules may be combined to produce extremely varied signalling pathways. Life is characterized by simplicity in design and colossal variation in form. The G-proteins' role in signal transmission in the cell is a shining example of this principle of variations on a theme that achieve the diversity necessary to maintain life.