Atomic force microscopy reveals the stoichiometry and subunit arrangement of 5-HT3 receptors

Nelson P. Barrera, Paul Herbert, Robert M. Henderson, Ian L. Martin, J. Michael Edwardson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The 5-HT3 receptor is a cation-selective ligand-gated ion channel of the Cys-loop superfamily. The receptor is an important therapeutic target, with receptor antagonists being widely used as antiemetics in cancer therapy. The two known receptor subunits, A and B, form homomeric 5-HT 3A receptors and heteromeric 5-HT3A/B receptors. The heteromeric receptor has the higher single-channel conductance and more closely mimics the properties of the native receptor. We have used atomic force microscopy to study the architecture of 5-HT3A and 5-HT 3A/B receptors. We engineered different epitope tags onto the A- and B-subunits and imaged receptors that were doubly liganded by anti-epitope antibodies. We found that, for the 5-HT3A/B receptor, the distribution of angles between antibodies against the A-subunit had a single peak at ≈144°, whereas the distribution for antibodies against the B-subunit had two peaks at ≈72° and 144°. Our results indicate that the subunit stoichiometry is 2A:3B and that the subunit arrangement around the receptor rosette is B-B-A-B-A. This arrangement may account for the difference between the agonist Hill coefficients and the single-channel conductances for the two types of receptor.

Original languageEnglish
Pages (from-to)12595-12600
Number of pages6
JournalProceedings of the National Academy of Sciences
Issue number35
Publication statusPublished - 30 Aug 2005


  • Ligand-gated ion channel
  • Receptor structure


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