| Species | Original | Mutated to | Mutation |
| Human | Pro 121 | Leu | |
| Rat Equivalent | Pro 96 | ||
| Mouse Equivalent | Pro 96 |
This mutation caused a markedly decreased rate of channel opening but little change in affinity of the resting state for ACh, but reduced affinity of the open channel and desensitized states.
This mutation has been correlated with myasthenic syndrome.