Question

Which of the following is different between stimulatory and inhibitory G proteins in the cyclic AMP pathway?

1) α subunit
2) β subunit
3) γ subunit
4) all of the above

Answer 1

The difference between stimulatory and inhibitory G proteins in the cyclic AMP pathway is in the α subunit, where stimulatory G proteins activate and inhibitory G proteins inhibit adenylate cyclase.

Step-by-step explanation:

In the cyclic AMP pathway, the difference between stimulatory and inhibitory G proteins lies in the α subunit. Stimulatory G proteins (designated as Gs) have an α subunit that activates adenylate cyclase, leading to increased levels of cAMP and subsequently triggering a cellular response such as the activation of protein kinase A (PKA) and gene transcription. Conversely, inhibitory G proteins (designated as Gi) have an α subunit that inhibits adenylate cyclase, thereby reducing cAMP levels and dampening the cellular response. It is the α subunit that determines whether the G protein will have a stimulatory or inhibitory effect on cAMP production; the β and γ subunits are common to both types of G proteins and do not differ between them.