Metabotropic receptors

From WikiLectures

Signal transduction at the GABA B receptor

Metabotropic receptors are receptors coupled to G-proteins that are designed for hydrophilic substances. The receptor is made up of a glycoprotein chain that passes through the membrane seven times. Signal molecules bind to the N-terminus of the chain.

Construction of receptors[edit | edit source]

Extracellular domain: ligand binding site

Transmembrane domain: a hydrophobic AMK that forms 7 α helices

Intracytoplasmic domain: interaction with G-proteins

G-protein: consists of three subunits: α,β,γ. G-proteins are bound to the receptor on the inside of the cytoplasmic membrane by means of lipid anchors (covalently bound fatty acids).

The ``α subunit binds the corresponding guanosine nucleotide and has GTPase activity.

Function of receptors[edit | edit source]

Activated state: bound GTP

Inactive Status: tied to GDP

Activation process: the ligand binds to the receptor, GDP is exchanged for GTP, the α subunit with GTP detaches and travels to the appropriate effector. Metabotropic receptors influence the production of second messengers.

A kind of α-subunit effector The second messenger Second messenger effects
Gs Activation of adenylate cyclase cAMP cAMP – activates protein kinase A, which phosphorylates proteins on the inner side of the membrane
Gi Inhibition of adenylate cyclase cAMP
Gq Phospholipase c Inositol triphosphate (IP3) and diacylglycerol (DAG) IP3 – opens calcium channels on the endoplasmic reticulum

DAG – activates protein kinase C

Examples of metabotropic receptors[edit | edit source]

  • dopamine receptor
  • GABA receptor – type B
  • glucagon receptors
  • secretin receptors
  • metabotropic glutamate receptor


Links[edit | edit source]

Related Articles[edit | edit source]

References[edit | edit source]

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