Question

4. a. we learned about 4 different types of membrane cell receptors. describe these different types and give a spesific example for each of them.

b. a certain patient as a mutation that nutrelizes the enzyme that is incharge of Myristoylation of proteins. which of the types of receptors that you descibed in question a will be affected by this mutation? what will be the effect? what is the role of Myristoylation? give as much details as possible.

Answer 1

a) The different types of cell-membrane receptors are

Ion channel linked receptors

These receptors bind a ligand and allow a particular ion to pass through them into the cytosol. They form a channel through the membrane by forming an extensive trans-memnbrane domain.

For example; the acetylcholine receptor is linked to a cation channel

G-protein linked receptors

Also called serpentine receptors since their transmembrane domain spans the membrane several times. G-proetin receptots when bound to a ligand, activate a G-protein, which then interacts with an ion channel or an enzyme.

eg; receptors of smell, hormones, neurotransmitters etc

Enzyme-linked receptors

enzyme linked receptors, are receptors linked directly to a enzyme, after a ligand bindsit initiates a specific activity of the bound enzyme. they have large extra cellular and intracellular domains. the membrane spanning region contains a single alpha helix spanning the entire membrane.

eg tyrosine kinase receptors

Q b) Myristoylation allows for the addittion of a myristic modification tp the target protein which allows for weak protein protein and protein lipid interaction. It is importtant in membrane localization and signal targeting

The reaction is done by the enzyme N-myritoyl transferase.

Since NMT is defective the protein that need to become myristoylated dont and dont end up localizing to the cytosol. this is important because this process helps a lot of membarane receptors to localize to the cytosol.

This affects various receptors like

G-protein- a signalling GTPase

PAK-2 a serine threonine kinase

hippocalcin- aneuronal calcium sensor

So this is an exmple of each type of cell membrane receptor that is affected by myritolation or lack of it thereof.