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Structural Features of the Ligand-binding Domain of the Serotonin 5HT3 Receptor
- Source :
- Journal of Biological Chemistry. 274:5537-5541
- Publication Year :
- 1999
- Publisher :
- Elsevier BV, 1999.
-
Abstract
- The nicotinic acetylcholine receptor (AChR) and the serotonin type 3 receptor (5HT3R) are members of the ligand-gated ion channel gene family. Both receptors are inhibited by nanomolar concentrations of d-tubocurarine (curare) in a competitive fashion. Chemical labeling studies on the AChR have identified tryptophan residues on the gamma (gammaTrp-55) and delta (deltaTrp-57) subunits that interact with curare. Comparison of the sequences of these two subunits with the 5HT3R shows that a tryptophan residue is found in the homologous position in the 5HT3R (Trp-89), suggesting that this residue may be involved in curare-5HT3R interactions. Site-directed mutagenesis at position Trp-89 markedly reduces the affinity of the 5HT3R for the antagonists curare and granisetron but has little effect on the affinity for the agonist serotonin. To further examine the role of this region of the receptor in ligand-receptor interactions, alanine-scanning mutagenesis analysis of the region centered on Trp-89 (Thr-85 to Trp-94) was carried out, and the ligand binding properties of the mutant receptors were determined. Within this region of the receptor, curare affinity is reduced by substitution only at Trp-89, whereas serotonin affinity is reduced only by substitution at Arg-91. On the other hand, granisetron affinity is reduced by substitutions at Trp-89, Arg-91, and Tyr-93. This differential effect of substitutions on ligand affinity suggests that different ligands may have different points of interaction within the ligand-binding pocket. In addition, the every-other-residue periodicity of the effects on granisetron affinity strongly suggests that this region of the ligand-binding site of the 5HT3R (and by inference, other members of the ligand-gated ion channel family) is in a beta-strand conformation.
- Subjects :
- Agonist
Binding Sites
DNA, Complementary
Base Sequence
Chemistry
medicine.drug_class
Stereochemistry
Tryptophan
Cell Biology
Ligands
Ligand (biochemistry)
Biochemistry
Protein Structure, Secondary
Nicotinic acetylcholine receptor
Receptors, Serotonin
Mutagenesis, Site-Directed
medicine
Humans
Amino Acid Sequence
Serotonin
Receptors, Serotonin, 5-HT3
Receptor
Molecular Biology
Ion channel
Acetylcholine receptor
Subjects
Details
- ISSN :
- 00219258
- Volume :
- 274
- Database :
- OpenAIRE
- Journal :
- Journal of Biological Chemistry
- Accession number :
- edsair.doi.dedup.....3a1dae0a87a3dae3f6de491dccf4a8af