nounIntermediate
Definition
A molecule that binds to a specific site on a receptor protein to trigger (agonist), block (antagonist), or modulate (allosteric modulator) a biological response.

Detailed Explanation

A molecule that binds to a specific site on a receptor protein to trigger (agonist), block (antagonist), or modulate (allosteric modulator) a biological response. Many ligands are peptides: insulin is a ligand for the insulin receptor, GLP-1 for the GLP-1 receptor, enkephalins for opioid receptors. Ligand–receptor binding follows the lock-and-key or induced-fit model, with binding strength measured by affinity (Kd). Drug development often begins with identifying or designing peptide ligands for disease-relevant receptors.

Key Facts

  • A molecule that binds to a specific site on a receptor protein to trigger (agonist), block (antagonist), or modulate (allosteric modulator) a biological response.
  • Many ligands are peptides: insulin is a ligand for the insulin receptor, GLP-1 for the GLP-1 receptor, enkephalins for opioid receptors.
  • Ligand–receptor binding follows the lock-and-key or induced-fit model, with binding strength measured by affinity (Kd).
  • Drug development often begins with identifying or designing peptide ligands for disease-relevant receptors.
Related Terms Receptor Affinity Agonist Is Not A Separate Term

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