Final answer:
Compounds such as hormones, neurotransmitters, and bacterial toxins specifically interact with GPCRs, leading to the activation of G-proteins and downstream cellular responses. GTP binding to the α-subunit of G-proteins and interaction with ion channels or enzymes are key steps in this signaling pathway.
Step-by-step explanation:
The compounds that exclusively act on GPCRs (G-protein coupled receptors) include a variety of ligands such as hormones, neurotransmitters, and even toxins produced by pathogenic bacteria. These compounds bind to the GPCR's extracellular domain, which in turn activates the coupled G-protein. This interaction can set off a cascade of cellular events, as the G-protein interacts with downstream effector proteins like ion channels or enzymes. The classic G-protein coupled pathway involves the binding of GTP in place of GDP on the α-subunit of the G-protein, leading to its activation and a subsequent cellular response, which might include the production of cAMP via the activation of adenylate cyclase or the opening of a chloride channel.
An example of a compound disrupting GPCR function is the choleragen toxin produced by Vibrio cholerae, which causes continuous activation of a G-protein and an uncontrolled chloride channel opening, leading to severe dehydration.