Wednesday, December 17, 2014

What is the a G-protein-coupled receptor?

The β2-adrenoreceptor is a G-protein-coupled receptor (GPCR)found in the cell membrane of
airway smooth muscle and lung epithelial and endothelial cells.

What is a G-protein coupled receptor?


G-protein coupled receptors are the largest family of cell-surface receptors. They are responsible for majority of cell responses to hormones and neurotransmitters, and are also important for senses such as sight, taste and smell.

General structure:

GPCRs have 7 transmembrane spanning regions. The N terminal of the protein is on the extracellular face, which binds to the ligand on the outside of the cell. The C terminal of the protein is found in the intracellular side of the membrane, which is linked to a G protein.


G proteins are made up of 3 subunit proteins; α,β and γ

     
 The general mechanism for GPCRs:
When an agonist molecule binds to the N terminal of the G-protein coupled receptor, it causes a conformational change in the receptor which activates the G protein. The G protein, normally bound to GDP in the inactive state, will now bind GTP. This then allows the G protein to futher activate secondary messenger proteins and allows signal transduction from outside to inside the cell.
 

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