Lecture 8 on receptor types

Question 1

Receptor types:

Answer 1

channel linked receptors

enzymatic receptors

G protein-coupled receptor

Question 2

Receptors as detectors

Answer 2

Receive signal and activate second messengers

Ion channels
◦Form a “pore” in the membrane

◦Only open when it’s signal particle is bound to the protein

◦Restrict movement of ions form one side of the membrane to another

G proteins
◦7 transmembrane domain containing proteins, embedded in the membrane
◦Associated with proteins on inner surface of the membrane that determine what type of response occurs
◦4 flavours (see later)

Question 3

Receptors as detectors 2

Answer 3

Enzyme coupled receptors

◦Single pass transmembrane receptors that “dimerise” in the membrane in response to ligand binding.
◦Activate each other to recruit intracellular proteins
◦Often result in the use of second messenger

Question 4

Ion Channel-Coupled Receptors

Answer 4

Transiently change the permeability of the plasma membrane when ligand binds to the receptor and enables it to open briefly

Question 5

These are just specialised transmembrane proteins

Answer 5

*The protein generates a pore in the membrane.

*Amino acids protruding into the channel can work as a selectivity filter to limit entry into the pore

*When the ligand binds to the receptor it changes the shape so that the pore can open to allow movement of appropriate ions through the pore

Question 6

Ion channel receptor examples

Answer 6

Question 7

G Protein-Coupled Receptors

Answer 7

➢Also known as GPCRs or G-proteins

➢General structure of G protein–coupled receptors are that they have seven-transmembrane domains

Question 8

Trimetric G proteins relay signals from GPCRs

Answer 8

Trimetric G proteins relay signals fromGPCRs

Question 9

G Protein-Coupled Receptors-2

Answer 9

Binding of the ligand to the receptor recruits the trimeric G-proteinsAssociation of the G-protein with the receptor leads to its activation and consequently activation of its enzyme partner

Question 10

Activation of G proteins by activated GPCRs

Answer 10

Activation of G proteins by activated GPCRs
1.Binding of the ligand to the GPRC leads to displacement of GDP from the inactive trimeric G protein complex.

2.Binding of GTP to the trimeric G protein leads to its activation & dissociation into ,β and ɣ subunits

Question 11

Activation of effector proteins associated with GPCRs.

Answer 11

General mechanism of the activation of effector proteins associated with GPCRs

Question 12

Different G proteins are activated by different GPCRs and in turn regulate different effector proteins

Answer 12

All effector proteins in GPRC pathways are either membrane-bound ion channels or enzymes that catalyse the second messengers