8/28 Class 3 Flashcards
What is the effector protein?
The protein that elicits second messengers and an effect in the cell.
Can you have more than one second messengers?
Yes! Here there are 3 different second messengers, DAG, IP3, and Calcium
Do all g proteins elicit the same response in a cell?
No, different g- proteins can activate different proteins, therefore having a different overall action/effect in the cell.
Describe the g-protein pathway involving Adenylyl Cyclase
Ligand binds to the receptor which releases the G protein with GTP on it.
That binds with the effector protein Adenylyl cyclase
Adenylyl cyclase spins ATP into cAMP
cAMP activates protein kinase A
This elicits a cellular response.
Describe the g-protein pathway involving Phospholipase C
Describe desensitization
Beta arrestin binds to the OH groups attached to the end of the carboxyl terminal on the 7TM protein and blocks further activity from occurring.
The protein gets “eaten” by the cell via a clathrin pit.
opt 1. drug breaks off of receptor: G-protein gets moved back to the cell surface to be reused.
opt.2 Lysosome merges with the ligand and the lysosome degrades the entire drug&receptor
What is clatherin?
A protein involved in endocytosis
What is endocytosis?
The taking in of matter by a cell (cell eats something)
What is a catalytic cell surface receptor?
A membrane bound, ligand activated active site that has an enzymatic component either directly associated with it, or the enzyme is built within itself.
Describe Recycling of a g-protein.
drug breaks off of receptor: G-protein gets moved back to the cell surface to be reused.
What is a kinase?
an enzyme that attaches a phosphate group
What is a phosphatase?
An enzyme that strips a phosphate group from a protein
what is an example of a catalytic cell surface receptor?
Tyrosine Kinase
What is tyrosine?
one of our 20 amino acids
What are the ligands that attach to Tyrosine kinases?
Growth Factors: EGF (Epidermal growth factor)
Adhesion Factors: When WBC bind to the surface of a blood vessel
What is dimerization?
Two monomers coming together
What does dimerization cause?
phosphorylation of the kinases which makes it act like a kinase enzyme
Describe the RTK process
- 2 ligands bind to 2 different RTK’s
- This makes the two monomers come together, and activates 6 ATP molecules.
- When they come together, they “activate” each other by becoming phosphorylated. The phosphates from the ATPs are added to the Tyrosines.
- It is now activated and can interact with effector proteins and create the downstream effects.
Where does the phosphate groups come from in the RTK process when phosphate are added to Tyrosines?
They are pulled from 6 ATP molecules
How are RTK’s different from G-proteins?
G proteins have to activate an enzyme where RTK’s are the enzyme
How are RTK’s the same as g-proteins?
They both are membrane bound, ligand activated, and eventually activate an effector protein.
What are voltage gated channels?
Pores in the cell’s surface that allow highly charged molecules to pass through the cell wall.
Where are voltage gated channels found within the body?
Neurons, muscle, endocrine cells
Which stage is this channel in?
Closed
Which stage is this channel in?
Activated
Which stage is this channel in?
Inactivated
Which stage is this channel in?
Deactivated
What is the cycle of a voltage gated channel?
closed, threshold, activated, inactivated, deactivated, circles back to closed again
What activates a voltage gated channel?
When a resting potential gets closer and closer to the firing potential, or threshold
What activates a ligand-gated ion channel?
a ligand binding to the receptor
What are the two subtypes of ligand-gated ion channels?
Inotropic
Metabotropic
How does a inotropic ligand-gated channel work?
The same as the Voltage gated except a ligand binds to it to activate it instead of a threshold.
How does a metabotropic ligand-gated channel work?
A ligand activates a GPCR which activates the channel