A G protein-coupled receptor is a cell-surface receptor that relays activation through a G protein on the intracellular side of the cell membrane. The activated G protein can regulate an enzyme or ion channel, so a GPCR supplies a concrete metabotropic receptor example: ligand recognition and the eventual response are connected through distinct components. Different G proteins couple to different targets. See Alberts et al., Molecular Biology of the Cell, 4th edition: signaling through G-protein-linked cell-surface receptors.
A protein family involved in regulation and signalling of activated receptors; recruitment can alter receptor coupling and trafficking.
The capacity of a signalling system to produce a maximal response without occupancy or activation of all receptors. It makes observed maximal response an unreliable direct measure of intrinsic ligand efficacy.
Preferential activation of one receptor-linked response relative to another, defined against a reference ligand and appropriate system controls. Different amplification or receptor reserve can mimic apparent bias.[ref]
An opioid receptor ligand, also called oliceridine, studied for differences between G protein activation and arrestin recruitment. Apparent signalling preference must be distinguished from low intrinsic efficacy.
A ligand that inhibits receptor activation by occupying the binding site used by an activating ligand.
The beta-2 adrenergic receptor is a G protein-coupled receptor whose ligand-dependent conformational populations have been studied by NMR spectroscopy and electron paramagnetic resonance.[ref]
Structural insights into the dynamic process of β2-adrenergic receptor signaling by Aashish Manglik and others. pp. 1101–1111, ligand and intracellular-partner effects on receptor dynamics
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G protein-coupled receptors (GPCRs) are a large family of membrane proteins that play a critical role in cellular signaling. These receptors are characterized by their ability to pass through the cell membrane seven times (hence they are also known as seven-transmembrane receptors). GPCRs respond to a variety of external signals, including hormones, neurotransmitters, and environmental stimuli, and are involved in many physiological processes.