Textures of Ligand Binding

Question 1

4 compounds that bind to class B GPCR

Answer 1

Alprenolol
Carazolol
ICI 118551
Propanolol

Question 2

2 compounds that bind to class C GPCR

Answer 2

Bucindolol

Carvedilol

Question 3

3 compounds that bind to class D GPCR

Answer 3

Atenolol
Metoprolol
Bisoprolol

Question 4

Agonist

Answer 4

Binds to the receptor and causes the same response as the natural hormone or peptide

Question 5

Antagonist

Answer 5

Binds to the receptor and prevents the normal response from occurring

Question 6

Inverse agonists

Answer 6

Bind to the receptor and cause the opposite response of the normal ligand
Stabilize the inactive form of the receptor

Question 7

Partial agonist

Answer 7

Binds to the receptor and causes the same response as the ligand, but not to the fully extent

Question 8

Competitive Antagonists

Answer 8

Bind to the same site on receptor as agonists
Inhibition can be overcome by increasing agonist concentration (reversible)
Primarily affect agonist potency
Clinically useful

Question 9

Non-competitive Antagonists

Answer 9

Bind covalently to the same site as agonist (irreversible) or to a site distinct from that of agonist (irreversible or reversible)
Inhibition cannot be overcome by increasing agonist concentration
Primarily affect efficacy
Limited clinical use

Question 10

Protean agonism

Answer 10

The phenomenon where a ligand behaves both as an agonist and antagonist at the same receptor depending on effector pathways

Question 11

Orthosteric

Answer 11

The primary binding site recognized by the endogenous agonist or hormone

Question 12

Allosteric

Answer 12

The drug can act at another site, distant from the orthosteric site, to activate a receptor

Question 13

Allosteric modulators

Answer 13

Characterized by coorperative binding, requiring the presence of endogenous agonists

Question 14

Ceiling effect

Answer 14

Maximal effect of the allosteric ligand can be controlled by the amount of orthosteric ligand

Question 15

Allosteric protomers

Answer 15

Receptor dimers where one receptor unit accepts the allosteric ligand to modulate the activity of the orthosteric ligand on the second receptor
So activation of the second protomer inhibits signalling by its partner

Question 16

Collateral efficacy

Answer 16

Describes selective not all-inclusive behaviours resulting from the binding of some ligands
Ligands can produce portions of the possible behaviours of receptors
Ligands have the ability to activate some, but not all, receptor pathways

Question 17

3 Reasons receptor-ligand interactions are important

Answer 17

1. Receptors mediate the actions of naturally occurring ligands and most drugs
2. Receptors determine the quantitative relationship between the concentration of ligand and the pharmacological effects
3. Receptors are responsible for specificity of drug action