Lecture 8 Flashcards
What is signal transduction?
When the ligand binds and other intracellular signalling events cause a further response
Describe how a ligand-gated ion channel and receptors with intrinsic enzymatic activity work
For ligand gated ion channels the gate defines specificity. These channels allow ions to move in and out of the cell. Receptors with intrinsic enzymatic activity work by phosphorylating the receptor after it has been activated.
Why are G coupled proteins so important?
They are the main target (other than enzymes) for therapeutics. The drugs that bind exert their effects directly. An example of how an antagonist can be used in this way are b-blockers in treating cardiovascular problems. GPCR’S respond to a large variety of stimuli, including ions, neurotransmitters and hormones. Sensory GPCR’s sense light.
What are the properties of a GCPR?
They are integral membrane proteins that have 7 domains of alpha helix polypeptides. The domains outside bind to the ligand.
The domains change their conformational change somewhat so that another protein can interact with it. An example is when the guanine nucleotide binding protein comes and binds and then is activated. At a resting stat it is GDP, when activated it is GTP.
Describe the mechanism for the activation of the G protein.
The G protein is made up of three subunits: alpha, beta and gamma. Together they are heterotrimeric, but the beta and gamma are tightly associated and considered as one. When the G protein is activated it exchanges GTP for GDP. This causes the alpha subunit to disassociate from the other two and they go on to perform separate functions in the cell. This stops when GTPase hydrolyses GTP back to GDP and the alpha beta/gamma subunits binds again.
