| Species | Original | Mutated to | Mutation |
| Human | Glu 59 | Lys | |
| Rat Equivalent | Asp 59 | ||
| Mouse Equivalent | Asp 59 |
When this mutation in both adult and fetal ACh receptors, surface binding was reduced to around 60%. When the open probability of the mutant receptors was tested using concentrations between 10 and 500 mM ACh, the activity occurred in clusters of openings from individual channels separated by longer closing periods. It was shown that the open probability for the mutant was lower than that of the wildtype. The Ec50 for the mutant was 58.4 mM ACh, and for the wildtype was 14.2 mM ACh. Both adult and fetal receptors with the E59K mutation are likely to have fewer and shorter channel activations.
This mutation has been correlated with myasthenic syndrome.