Cell signalling 2 Flashcards
What are the three main classes of cell surface signalling receptor?
Ion channel-coupled receptors, G-protein coupled receptors and enzyme-coupled receptors.
What does changes in protein conformation allow?
Switching between active and inactive states in a reversible manner.
What are common conformation switches used in signalling pathways?|
Protein phosphorylation, GTP-binding protein.
What are G protein coupled receptors?
7-pass transmembrane proteins. They are the largest receptor.
What is the state of the G protein in resting state?
The trimeric G protein is tethered to the inner leaflet of the plasma membrane and the alpha subunit is associated with a molecule of GDP.
What are the alpha subunits of G-proteins?
GTPase enzymes.
What happens when a signalling molecules binds to the G-protein coupled receptor?
It changes the receptor conformation and allows binding of the G protein to the receptor.
What happens after a signalling molecule binds to a G-protein coupled receptor?
The G protein interaction alters the conformation and promotes the release of GDP which is replaced by GTP.
What happens after GDP is released from the G protein coupled receptor?
There is a further conformational change in the alpha subunit which is activated and disassociates both from the beta gamma complex and from the receptor.
What regulates the cardiac pacing?
The vagus nerve.
What can active alpha/GTP subunits associate with?
Specific target enzymes to activate their activity.
What else does interaction of the G-protein coupled receptor with its target enzyme do?
It activates the GTPase activity of the alpha/GTP subunit. After a short delay the alpha subunit hydrolyses GTP to GDP and restores the inactive alpha subunit conformation causing it to release from the target enzyme. The resting state is now restored.
What do GsG proteins do?
They raise the levels of cAMP.
What do Gq G proteins do?
Raise levels of Ca2+ ions.
What does alpha Gs do?
It stimulates adenylyl cyclase.
