heterotrimeric G-protein complex

Definition

Target type: cellularcomponent

Any of a family of heterotrimeric GTP-binding and hydrolyzing proteins; they belong to a superfamily of GTPases that includes monomeric proteins such as EF-Tu and RAS. Heterotrimeric G-proteins consist of three subunits; the alpha subunit contains the guanine nucleotide binding site and possesses GTPase activity; the beta and gamma subunits are tightly associated and function as a beta-gamma heterodimer; extrinsic plasma membrane proteins (cytoplasmic face) that function as a complex to transduce signals from G protein-coupled receptors to an effector protein. [ISBN:0198547684]

Heterotrimeric G proteins are a family of proteins that act as molecular switches in signal transduction pathways. They are composed of three subunits: alpha (α), beta (β), and gamma (γ). The α subunit binds guanine nucleotides (GTP or GDP) and is responsible for the activation of downstream signaling pathways. The βγ dimer, which is tightly associated with the α subunit, plays a role in regulating the activity of the α subunit and interacting with effector proteins.

The cellular component of the heterotrimeric G-protein complex is the plasma membrane. The α subunit is anchored to the inner leaflet of the plasma membrane by a lipid modification, such as myristoylation or palmitoylation. The βγ dimer is also associated with the plasma membrane, although the exact mechanism of its membrane association is not fully understood.

The location of the G-protein complex at the plasma membrane is crucial for its function. It allows the complex to interact with receptors that are activated by extracellular signals, such as hormones, neurotransmitters, and light. Upon activation of the receptor, the G-protein complex is activated, leading to the dissociation of the α subunit from the βγ dimer. The activated α subunit then interacts with downstream effector proteins, such as adenylyl cyclase or phospholipase C, to initiate signal transduction pathways. The βγ dimer also plays a role in signal transduction by interacting with effector proteins, such as ion channels and other signaling proteins.

In summary, the cellular component of the heterotrimeric G-protein complex is the plasma membrane, where it interacts with receptors and effector proteins to mediate signal transduction pathways.'
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Proteins (6)

Compounds (169)