Effect of background mutations, 11-Gly loop-C construct
| Constructs | f0 | ±SE | b0 | ±SE | E0 | ±SE | Fold change E0 | Fold change E2cho | n |
| αA96H | 241 | 16 | 19,360 | 1,869 | 0.013 | 0.01 | — | — | 4 |
| +εS450W | 438 | 24 | 2,536 | 151 | 0.173 | 0.01 | 13.3 | 9.9 | 3 |
| +βT456F | 478 | 4 | 5,341 | 298 | 0.090 | 0.01 | 6.9 | 5.2 | 2 |
| +εL269F | 2,818 | 1,308 | 2.154 | 165.7 | 179.0 | 1 |
| Constructs | f0 | ±SE | b0 | ±SE | E0 | ±SE | Fold change E0 | Fold change E2cho | n |
| αA96H | 241 | 16 | 19,360 | 1,869 | 0.013 | 0.01 | — | — | 4 |
| +εS450W | 438 | 24 | 2,536 | 151 | 0.173 | 0.01 | 13.3 | 9.9 | 3 |
| +βT456F | 478 | 4 | 5,341 | 298 | 0.090 | 0.01 | 6.9 | 5.2 | 2 |
| +εL269F | 2,818 | 1,308 | 2.154 | 165.7 | 179.0 | 1 |
11-Gly, a loop-C construct with 11 glycine residues substituted at positions α188–α198 in both α subunits (WT mouse sequence VFYSCCPTTPY; see Fig. 3). The mutation αA96H was present in all constructs to increase constitutive activity. +, the additional background mutation. Fold changes are relative to the no-additional-background construct, either without agonists (E0, 11-Gly construct) or in 20 mM choline (E2cho; WT-binding sites). n, number of patches. The effect of the added background mutation is similar with 11-Gly or WT C loops. Fold change E2choline values are from Mitra et al. (2004; εS450W and βT456F) and Jha et al. (2009; εL269F).