Action of alpha-subunit of G protein is:
**Core Concept**
The alpha-subunit of G protein plays a crucial role in signal transduction by interacting with downstream effectors to modulate various cellular processes. Upon activation by G protein-coupled receptors (GPCRs), the alpha-subunit dissociates from the beta-gamma dimer and activates or inhibits specific effectors, leading to a cascade of downstream events.
**Why the Correct Answer is Right**
The alpha-subunit of G protein is responsible for activating or inhibiting downstream effectors, such as adenylyl cyclase, phospholipase C (PLC), or potassium channels. Upon activation, the alpha-subunit binds to and activates these effectors, leading to an increase in intracellular cAMP (adenosine monophosphate) or an increase in intracellular calcium levels. This, in turn, triggers various cellular responses, including changes in gene expression, metabolism, and ion channel activity.
**Why Each Wrong Option is Incorrect**
* **Option A:** This is not a correct description of the alpha-subunit's action.
* **Option B:** This is not a correct description of the alpha-subunit's action.
* **Option D:** This is not a correct description of the alpha-subunit's action.
**Clinical Pearl / High-Yield Fact**
The alpha-subunit of G protein is a key regulator of various cellular processes, including hormone secretion, muscle contraction, and neurotransmission. Dysregulation of G protein signaling has been implicated in several diseases, including cancer, cardiovascular disease, and neurodegenerative disorders.
**Correct Answer: C. Activation of downstream effectors.**