Receptor Mechanism II Flashcards
What is the G protein-coupled receptor superfamily? What are their structure like and how does it function?
These are a range of things that activate GPCR of which there are about 800
The agonist tends to bind in or around the amino terminus of the trans-membrane domain
This protein has a long C terminus and within this there is a site where it interacts with a second protein that gives it its name
The G proteins are a trimer; a big a, a y and a b all exist in a basal state and the a subunit has GDP
When the agonist binds, it causes a shift in the affinity and the a subunit now binds GTP becomes alive and dissociates from the b,y and interacts with enzymes to reach its effect
The GPCR is also known as a heptahelical receptor or 7TM receptor
The a subunit is subdivided into a\/s, a\/i, a\/q/11 and a\/12
The names are based upon the type of enzyme that the alpha subunit interacts with
What does the Gq11 cause? (How does GPCR work)
Gq11= increased phospholipase C activity
This enzyme has for a substrate a membrane phospholipids called phosphotidylglinositol bisphophate (PIP2), found in the membrane
The PLC(-b) then cleaves it into inositol trisphosphate (IP3) which is water soluble and diacyl glycerol (DAG)
DAG has a no. of jobs but it also turns on protein kinase C
IP3 binds to its own receptor, located on internal organelles, such as the endoplasmic reticulum that have a ton of Ca2+ and, by binding, causes Ca2+ to be released
If it is a muscle cell it will contract, if it’s a secretory cell it will cause enzymes to be released etc.
All of this is a big single amplification process
