G-protein alpha-subunit binding

Definition

Target type: molecularfunction

Binding to a G-protein alpha subunit. The alpha subunit binds a guanine nucleotide. [GOC:hjd]

G-protein alpha-subunits are key components of heterotrimeric G proteins, which act as molecular switches in signal transduction pathways. They bind to and are activated by G protein-coupled receptors (GPCRs) upon ligand binding. The alpha subunit, upon activation, dissociates from the beta-gamma dimer and interacts with downstream effector proteins, such as adenylyl cyclase or phospholipase C. This interaction initiates a cascade of intracellular signaling events that ultimately lead to physiological responses.

The molecular function of G-protein alpha-subunit binding encompasses several key aspects:

1. **Ligand-induced activation:** Upon binding of a ligand to a GPCR, the receptor undergoes a conformational change that promotes interaction with the alpha subunit. This interaction triggers the exchange of GDP for GTP on the alpha subunit, leading to its activation.

2. **Dissociation from the beta-gamma dimer:** The GTP-bound alpha subunit undergoes a conformational change that disrupts its association with the beta-gamma dimer, allowing it to interact with downstream effectors.

3. **Effector protein binding:** The activated alpha subunit interacts with specific effector proteins, such as adenylyl cyclase or phospholipase C. This interaction activates the effector protein, initiating downstream signaling cascades.

4. **GTP hydrolysis and inactivation:** The alpha subunit possesses intrinsic GTPase activity, which hydrolyzes the bound GTP to GDP. This hydrolysis event leads to the inactivation of the alpha subunit and its reassociation with the beta-gamma dimer, returning the G protein to its inactive state.

5. **Regulation of downstream signaling:** The binding of the alpha subunit to effector proteins regulates the activity of these proteins, ultimately influencing downstream signaling pathways.

The molecular function of G-protein alpha-subunit binding is therefore crucial for the proper functioning of GPCR signaling pathways and plays a vital role in a wide range of physiological processes, including hormone regulation, neurotransmission, and sensory perception.'
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Proteins (12)

Compounds (981)