G Protein-Coupled Signal Transmission Pathways

An example of a transmembrane receptor that registers sensory signals is rhodopsin. Rhodopsin is a sensory receptor that plays a role in vision, by receiving light signals and converting them into intracellular signals. 

In addition to reception of hormonal signals by transmembrane receptors or nuclear receptors, the cell also has other means to conduct signals into the cell interior. 

Another mechanism uses changes in membrane potential. A change in membrane potential induces the opening of an ion channel and ions cross the membrane (see Chapter 16). In this case, the change of the ion s mUieu is the intracellular signal. Ion channels with an open state regulated by changes in membrane potential are known as 

Transmembrane receptors have the following roles in signal transduction  

Transmembrane receptors are integral membrane proteins, i.e., they possess a structural portion that spans the membrane. An extracellular domain, a transmembrane domain and an intracellular or cytosolic domain can be differentiated within the structure (Fig. 5.2a). 

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