Receptor conformational changes during

The 3 isozymes are activated by G protein-coupled receptors through two different mechanisms [2]. The first involves activated a-subunits of the Gq family of heterotrimeric G proteins (Gq, Gn, Gi4, G15/16). These subunits activate the (31, (33 and (34 PLC isozymes through direct interaction with a sequence in the C terminus. The domain on the Gqa-subunit that interacts with the (3 isozymes is located on a surface a-helix that is adjacent to the Switch III region, which undergoes a marked conformational change during activation. The second mechanism of G protein activation of PLC 3 isozymes involves (3y-subunits released from Gi/0 G proteins by their pertussis toxin-sensitive activation by certain receptors. The 3y-subunits activate the 32 and 33 PLC isozymes by interacting with a sequence between the conserved X and Y domains. 

Conformational changes during lateral diffusion to the receptor site within the bilayer. In some cases the optimal conformation of the drug may be formed only within the lipid environment. 

Bissantz C. Conformational changes of G protein-coupled receptors during their activation by agonist binding. I Recept Signal Transduct Res 2003 23(2-3) 123-153. 

The acetyl choline receptor is a ligand-gated ion channel that allows cations to flow out of the neuron to initiate an action potential during neurotransmission (Fig. 9-6). When the receptor binds acetylcholine, a conformational change of the receptor opens a membrane channel that conducts ions. 

The sequences of events that occur during activation of adenylate cyclase after receptor occupancy are shown in Figure 6.3. This scheme thus shows activation of a Gofc-type protein (i.e. a process that leads to the activation of adenylate cyclase), whereas similar processes will occur with a Ga protein, except that the interaction with adenylate cyclase will result in its inactivation. In the same way, activation of phospholipases by mobile Ga-type subunits will occur via similar mechanisms. In the unstimulated state, Gas (or Gcq) is bound to GDP. Binding of the receptor with its agonist induces a conformational change in the receptor that activates its G-protein. This stim-... 

Ward, S. D., Hamdan, F. F., Bloodworth, L. M., and Wess, J. (2002). Conformational changes that occur during M3 muscarinic acetylcholine receptor activation probed by the use of an in situ disulfide cross-linking strategy. J. Biol. Chem. 277, 2247-2257. 

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