The _______ - subunit of most heterotrimeric G-proteins binds the guanine nucleotides and acts as a _________.
a. beta, ATPase
b. gamma, GTPase
c. alpha, ATPase
d. gamma ATPase
c. alpha, GTPase
I think the right answer is "E" but not sure please help
E is correct. The alpha subunit has the GTPase activity, the beta, gamma subunits are tightly associated and do not dissociate when activated.
To arrive at the correct answer, we need to understand the roles of the different subunits of heterotrimeric G-proteins.
Heterotrimeric G-proteins consist of three subunits: alpha, beta, and gamma. The alpha subunit binds and hydrolyzes guanine nucleotides (specifically GTP) and is responsible for transmitting the signal downstream. The beta and gamma subunits are tightly associated and do not dissociate when activated. They act as a functional unit and are involved in regulating the activation and interaction of the alpha subunit with other signaling molecules.
In the provided options, the correct answer is c. alpha, GTPase. The alpha subunit of most heterotrimeric G-proteins binds to guanine nucleotides, specifically GTP, and possesses GTPase activity. This means that it can hydrolyze GTP to GDP, which is an essential step in terminating the signaling cascade.
Therefore, the correct answer is c. alpha, GTPase.