TABLE 1.
Summary of thermodynamics and kinetics of EmrE bound to range of tetrahedral and planar ligands
| Ligand | Binding constant (KdpH7)a | ΔH | n | Interconversion rate (kconf) | Relative transportb | LogP |
|---|---|---|---|---|---|---|
| μm | kJ/mol | s−1 | ||||
| MeTPP+ | 130 ± 20 | −12.7 ± 0.2 | 0.60 ± 0.04 | 190 ± 80 | 1 | 1.8 ± 0.1 |
| EtTPP+ | 21.8 ± 0.7 | −16.6 ± 0.2 | 0.57 ± 0.04 | 25 ± 5 | 2 | 1.9 ± 0.1 |
| TPP+ | 0.45 ± 0.01 | −22 ± 1 | 0.49 ± 0.05 | 4.4 ± 0.4, 4.7 ± 0.6c | 4 | 2.2 ± 0.1 |
| DPhTPP+ | 0.16 ± 0.02 | −39.4 ± 0.3 | 0.53 ± 0.05 | 0.4 ± 0.1 | 5 | 3.0 ± 0.2 |
| MBTPP+ | 0.04 ± 0.01 | −38 ± 2 | 0.544 ± 0.009 | 13 ± 3 | 3 | 2.5 ± 0.1 |
| DQ2+ | 100 ± 20 | −5.7 ± 0.3 | 0.58 ± 0.02 | 11 ± 2 | N/A | 3.4 ± 0.1 |
| PP2+ | 90 ± 10 | −16.3 ± 0.7 | 0.58 ± 0.06 | 13 ± 3c | N/A | 4.3 + 0.5/−1.0 |
a Observed binding constant from ITC at pH 7, 45 °C.
b Determined via in-cell assay. Ranked 1 through 5, from fastest to slowest EmrE-dependent ethidium efflux in the presence of each competing ligand.
c Reconstituted into DMPC/DHPC isotropic bicelles.