Tryptophan participates in which type of interaction in the muscarinic binding site?

Tryptophan participates in which type of interaction in the muscarinic binding site?

• A. Ionic bonding
• B. Covalent bonding
• C. Van der Waals
• D. Hydrogen bonding

Answer: (C)

Tryptophan’s aromatic side chain provides a nonpolar, bulky surface that stabilizes ligands primarily through close, noncovalent contacts known as van der Waals interactions. In the muscarinic binding pocket, these dispersion and induced-dipole forces between the ligand and the tryptophan residue are the dominant stabilizing contacts, especially in a largely hydrophobic pocket. Ionic or covalent bonds would require charged or reactive groups and are not typical for reversible GPCR–ligand binding. Hydrogen bonding can occur with some residues, but the main role of tryptophan here is to engage in van der Waals contacts to help position and stabilize the ligand.

Tryptophan’s aromatic side chain provides a nonpolar, bulky surface that stabilizes ligands primarily through close, noncovalent contacts known as van der Waals interactions. In the muscarinic binding pocket, these dispersion and induced-dipole forces between the ligand and the tryptophan residue are the dominant stabilizing contacts, especially in a largely hydrophobic pocket. Ionic or covalent bonds would require charged or reactive groups and are not typical for reversible GPCR–ligand binding. Hydrogen bonding can occur with some residues, but the main role of tryptophan here is to engage in van der Waals contacts to help position and stabilize the ligand.