Even the simplest organisms can detect and respond to events in their ever-changing environment. Similarly, within a multicellular organism, cells are surrounded by an extracellular environment from which signals are received and responded to. Extracellular events are decoded and transmitted to relevant parts of individual cells by way of a series of activation/deactivation steps involving many intracellular molecules. This relay of information along molecular pathways is called signal transduction; it is sometimes also simply referred to as ‘signalling’.
The molecular models shown in this chapter were produced using the Brookhaven protein data base (pdb) files indicated in the figure legends. These files can be downloaded, viewed and manipulated using a suitable molecular viewing programme, such as Viewerlite tm.
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