Table 1.
The cation binding affinities for 7E15 variants
| Protein | Residues | Charge | Kd | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 15 | 56 | 58 | 62 | 64 | Tb3+ (μM)a | La3+ (μM)a | Ca2+ (mM)b | ||
| CD2 | N | E | L | D | K | -1 | NB | NB | NB |
| EEDDD | E | E | D | D | D | -5 | 0.4 ± 0.2 | 0.5 ± 0.1 | 0.10 ± 0.05 |
| EEDDE | E | E | D | D | E | -5 | 0.8 ± 0.2 | 0.7 ± 0.1 | 1.1 ± 0.4 |
| EEDDN | E | E | D | D | N | -4 | 6.3 ± 0.6 | 2.2 ± 0.4 | 2.1 ± 0.5 |
| EEDDQ | E | E | D | D | Q | -4 | 14 ± 3 | 3.2 ± 0.7 | 0.7 ± 0.2 |
| EENDN | E | E | N | D | N | -3 | > 30 | > 15 | > 10 |
| NENDN | N | E | N | D | N | -2 | NB | NB | NB |
Buffer condition: 20 mM PIPES-10 mM KCl, pH 6.8. NB: No observed binding. a: from Tb3+-FRET. b: from NMR HSQC.