The Intracellular Domain of Membrane Receptors

Two basic mechanisms are used for conduction of the signal to the inner side of the 

Starting from the activated receptor, a large number of reactions can be set in motion (Fig. 5.5). One main route of signal transmission takes place by activation of G proteins, another via activation of tyrosine-specific protein kinases, and a further route is via activation of ion channels. In the further course of G protein-mediated signal transmission, secondary diffusible signals are often formed the second messenger molecules (see Chapters 3 and 6). These function as effectors and activate further enzyme systems in the sequence, especially protein kinases. 

The activated receptor can also associate with adaptor molecules, which serve as coupling elements for further signal proteins. 

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