TK receptors Flashcards
what activates the tyrosine?
phosphate being added
what usually happens when a phosphate gets removed?
something is going to be slowed down / stopped
what is the basic structure of a kinase linked receptor?
- has an extracellular region (N terminal chain)
- has an extracellular region where the messenger binds
- has a C-terminal chain inside the cell membrane
- a single chain
- a single hydrophobic region which crosses the membrane as an alpha helix of 7 turns
what does a dual role mean?
- they act as receptors and enzymes in 1 molecule
what are cytokines?
proteins produced by the immune system to regulate inflammation
where does the ligand bind?
the N terminal
where is the catalytic binding region?
the C terminal
what kind of ligand is EGF?
a bivalent ligand (it can bind 2 receptors at the same time)
during the resting state, where is the active site?
the active site is hidden because the receptor has no catalytic activity.
what happens when the ligand binds?
the receptor changes shapes and reveals the active site on the C-terminal chain
what are the steps of the signalling mechanism
the ligand binds, the receptor changes shape and reveals the active site on the C-terminal chain, the tyrosine is phosphorylated
what does dimerisation mean?
the active site on each half of the receptor dimer catalyses the phosphorylation of the tyrosine residues in the other half. if dimerisation doesnt occur then phosphorylation cannot take place
what is an example of a TK receptor?
EGF receptor
what is a bivalent ligand? give an example of one
a ligand that can bind 2 receptors at the same time, EGF is a bivalent ligand
how do receptors that do not have catalytic activity activate a TK enzyme?
Some TM kinase receptors can bind ligands and dimerise but do not have catalytic activity in their C-terminal chain
Once they have dimerised they can bind and activate a TK enzyme from the cytoplasm.
These receptors are known as tyrosine kinase linked receptors
what is an example of a receptor that has no catalytic activity?
the growth hormone receptor
what happens after phosphorylation of the kinase receptor?
the phospho-tyrosine groups act as binding sites for signalling proteins. these molecules can also become phosphorylated and act as further binding sites.
what happens when the signalling molecule binds to the phosphorylated tyrosine region?
it initiates a cellular response
what does the type of signalling depend on?
The type of signalling that results depends on which proteins have managed to bind to the kinase receptors
what is usually the starting point for phosphorylation cascades?
signalling
