| Species | Original | Mutated to | Mutation |
| Human | Ile 66 |
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| Rat Equivalent | Ile 71 |
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| Mouse Equivalent | Ile 71 | Ala |
Twenty six residues (I71, Y73,W90, R92, N128, E129, Y143, Y153, T179, T181, S182,W183, L184, W195, V201, R202, S203, S206, I207, F226, I228, D229, I230, Y234, E236, K238) were replaced by either alanine or a residue with similar physicochemical properties to the native residue, to examine their roles in docking of [3H]granisetron into the 5-HT3A receptor binding site. Mouse 5-HT3A receptors were expressed in HEK293 cells and homology modeling, ligand-docking and radioligand binding were used.
The I71A and I71L mutations did not significantly altered the affinity of the antagonist [3H]granisetron. The table below lists conservative and non-conservative substitutions that either both, or individually affected [3H]granisetron binding.
| Receptor | [3H]granisetron binding (Kd) |
| WT | 0.31+/-0.04 |
| W90A* | NB |
| W90Y* | 0.90 +/- 0.06 |
| R92A* | 1.80 +/- 0.40 |
| R92K | 1.00 +/- 0.30 |
| E129A* | NB |
| E129D* | NB |
| Y153A* | 2.36 +/- 0.53 |
| Y153F | 0.90 +/- 0.20 |
| T179A* | 3.20 +/- 0.10 |
| T179S | 0.38 +/- 0.20 |
| S181A* | 0.12 +/- 0.04 |
| S181S | 0.58 +/- 0.10 |
| S182A* | 1.00 +/- 0.20 |
| S182T* | 1.80 +/- 0.09 |
| W183A*/Y* | NB |
| L184A* | 4.11 +/- 0.94 |
| L184I* | 0.71 +/- 0.05 |
| W195A* | 5.08 +/- 0.88 |
| W195Y* | 8.70 +/- 2.40 |
| S203A* | 0.08 +/-0.02 |
| S203T | 0.26 +/- 0.11 |
| S206A* | 1.67 +/- 0.27 |
| S206T* | 4.40 +/- 0.49 |
| I228A* | 1.40 +/- 0.30 |
| I228N | 0.30 +/- 0.05 |
| D229A* | 3.80 +/- 0.26 |
| D229E* | 0.11 +/- 0.03 |
| I230A | 0.30 +/- 0.10 |
| I230N* | 1.70 +/- 0.40 |
| Y234A* | NB |
| Y234F | 1.30 +/- 0.36 |
NB, No binding
* significantly different from the WT 5-HT3A receptor