| Species | Original | Mutated to | Mutation |
| Human | Cys 227 | Phe | |
| Rat Equivalent | Asn 232 | ||
| Mouse Equivalent | Asn 232 |
Rush R, Kuryatov A, Nelson ME, Lindstrom J. First and second transmembrane segments of alpha3, alpha4, beta2, and beta4 nicotinic acetylcholine receptor subunits influence the efficacy and potency of nicotine. Mol Pharmacol. 2002 Jun;61(6):1416-22.