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In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose.
Ligands include:
Substrates
Inhibitors
Activators
Signaling lipids
Neurotransmitters
A ligand that can bind to and alter the function of the receptor that triggers a physiological response is called a receptor agonist.
Endogenous agonists:
Examples of agonists:
- acts as a 1alpha,25(OH)(2)D(3) superagonist of Vitamin D on Vitamin D receptor and exhibits both antiproliferative and prodifferentiating properties in vitro.
- in Transport inhibitor response 1 (3c6o). Water molecules are shown as red spheres.
- of human Bile acid receptor ligand-binding domain (deeppink) complex with non-steroidal agonist, nuclear receptor coactivator 1 peptide (cyan) and sulfate ions (PDB entry 3ruu). [1]
Ligands that bind to a receptor but fail to activate the physiological response are receptor antagonists.
- participates directly in agonist/competitive antagonist binding, affects activation gating, and is the portion that forms the 'middle' layer.
- in the structure of Glutamate receptor (GluA2).
- The small molecule [2], was studied as a treatment for stroke because it had demonstrated neuroprotective efficacy in experimental models of stroke and tolerability in healthy volunteers; however, in a multicenter, double-blind, randomized, placebo-controlled phase II trial, it was found to have significant sedative effects in patients with acute stroke which precludes its further development as a neuroprotective agent[3].
