Lecture 12- GTPase Focus Flashcards
What causes GTPAse to hydrolyze it’s bound for GTP, and thus INACTIVATING its signal?
GTPase activating proteins (GAPs)
When a GTPase is bound to GTP, it is…
On/active
What do GTPase activating proteins (GAPs) do?
They cause GTPase to hydrolyze it’s bound to GTP, this INACTIVATING its signal.
In other words, it increases the rate of GTP hydrolysis, thereby inactivating its signal.
G proteins are comprised of what?
A complex of three proteins, called the “Trimeric G Protein.”
What activates GTPases?
Guanine nucleotide exchange factors (GEFs)
When a GTPase hydrolyzes bound GTP, it is…
Off/inactive.
What is counterintuitive about GTPase activating proteins (GAPs)?
It is called an activating protein but when it causes GTPase to hydrolyze bound GTP, it INACTIVATES the signal.
Why does the G-protein-linked receptor act like a GEF?
After a signal molecule arrives to bind to the G-protein linked receptor, The receptor causes the alpha subunit to exchange GDP for GTP, just like a GEF does.
Similar to GTPase, what is active when bound to GTP, and inactive when bound to GDP?
The alpha subunit within the Trimeric G protein complex.
What is the function of GTPase?
To bind and hydrolyze GTP.
The Trimeric G protein, a complex of three protein subunits, is inside the…
G-protein-linked receptor
What are the steps for the alpha subunit generating an intracellular signal?
1) signal molecule binds to G-protein-linked receptor
2) conformational change, which causes the G-protein-linked receptor to make the alpha subunit exchange GDP for GTP
3) once the alpha subunit has bound GTP, the alpha subunit can disassociate from the gamma and bats subunits, and then ACTIVATE SPECIFIC ENZYMES to generate intracellular signals
What is the alpha subunit?
It is a GTP binding protein that is inactive when bound to GDP, and active when bound to GTP.
What do GEF’s do?
Try catalyze exchange of GDP for GTP, thereby activating GTPases.
