Taste light-induced

There is another large class of receptors whose occupancy by an agonisf leads to inhibition of adenylate cyclase. These include the tt2 adrenergic receptors, receptors for acetylcholine, adenosine, prostaglandin E2 (Chapter 21), somatostatin, and some receptors for dopamine. Their responses are mediafed by inhibitory proteins Gj, which closely resemble Gg in their sizes, amino acid sequences, and heterotrimeric structures, but which inhibit adenylate cyclase when activated. A clear distinction between the Gg and Gj proteins is evident in the fact that Gg is irreversibly activated by the action of cholera toxin, while G loses its ability to respond to occupied receptors when modified by the action of Pertussis toxin (Box 11-A). A specialized heterotrimeric G protein known as transducin mediates the light-induced activation of a cyclic GMP phosphodiesterase in the retina " (see Chapter 23). Its a subunit is designated aj. The related gustducin is found in taste buds. ... 

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