Table 2.
Average anomalous difference densitya
| Br− conc. | Sint | Scen | Sext | No. of data sets |
|---|---|---|---|---|
| ‘Open conformation' affinity | ||||
| 0 mM | 1.9±0.7 | 2.3±0.4 | 2.0±0.4 | 2 |
| 1 mM | 0.9±0.7 | 1.0±0.3 | 1.6±1.4 | 2 |
| 5 mM | 3.3±1.5 | 3.6±1.1 | 5.0±1.6 | 2 |
| 10 mM | 4.2±0.7 | 4.6±1.1 | 9.6±1.3 | 2 |
| 25 mM | 6.1±3.1 | 10.6±3.3 | 13.5±4.0 | 2 |
| 75 mM | 7.7±0.7 | 12.3±1.5 | 14.3±0.4 | 1 |
| 250 mM | 10.1±1.1 | 11.0±4.1 | 11.9±3.2 | 2 |
| ‘Closed conformation' affinity | ||||
| 1 mM | 1.5±0.8 | 1.0±0.3 | — | 1 |
| 5 mM | 2.9±0.9 | 5.9±0.9 | — | 2 |
| 25 mM | 5.1±0.4 | 11.1±0.0 | — | 1 |
| 400 mM | 8.7±0.6 | 11.4±2.7 | — | 1 |
| TRPL | — | — | 10.2±1.8 | 2 |
| ‘Open conformation' selectivityb | ||||
| 75% Br− | 7.7±2.3 | 4.1±1.6 | 8.1±2.7 | 2 |
| 50% Br− | 6.6±1.0 | 2.0±1.6 | 4.0±0.9 | 2 |
| 25% Br− | 3.0±0.6 | 1.4±0.8 | 2.8±0.9 | 2 |
| ‘Closed conformation' selectivityb | ||||
| 75% Br− | 10.0±0.1 | 6.8±0.8 | — | 1 |
| 50% Br− | 5.4±0.0 | 3.5±0.1 | — | 1 |
| 25% Br− | 3.2±1.1 | 2.1±0.8 | — | 1 |
| ‘Open conformation' |
‘Closed conformation' |
|||
| |
KDBr− (mM) |
KDBr−/KDCl− |
KDBr− (mM) |
KDBr−/KDCI− |
| Affinities/selectivitiesc | ||||
| Sint | 22.8 | 0.67 | 16.8 | 0.57 |
| Scen | 13.3 | 4.3 | 4.8 | 2.0 |
|
Sext |
6.2 |
1.6 |
— |
— |
| a The respective peak heights of the binding sites Sint, Scen and Sext are averaged between the two subunits in the asymmetric unit and between different data sets (Table I). The averages and the standard deviations are listed. | ||||
| b For the ‘open conformation' and ‘closed conformation' selectivity experiments, the Br− concentration in solution is given in % of a combined Cl−+Br− concentration of 250 mM. | ||||
| c Br− affinities and Br−/Cl− selectivities were obtained from a fit of the peak heights to equations (1) and (2), respectively. | ||||