TABLE 2.
Relative lipid binding constants for KcsA determined from fluorescence quenching data
| Binding constant K relative to DOPC
|
|||
|---|---|---|---|
| Lipid X | K+ concentration (mM) | X/BrPC | BrX/DOPC |
| Phosphatidylethanolamine | 0 | 0.57 ± 0.09 | 0.69 ± 0.10 |
| Phosphatidylserine | 0 | 0.83 ± 0.16 | 2.16 ± 0.17 |
| 500 | 1.27 ± 0.22 | 1.43 ± 0.16 | |
| Phosphatidic acid | 0 | 1.38 ± 0.26 | 1.95 ± 0.22 |
| 500 | 1.47 ± 0.36 | 1.67 ± 0.14 | |
| Phosphatidylglycerol | 0 | 1.26 ± 0.06 | 1.66 ± 0.20 |
| Cardiolipin | 0 | 0.41 ± 0.09 | 1.61 ± 0.23 |
Lipid binding constants relative to DOPC were determined by fitting quenching data for KcsA in mixtures of lipid X with BrPC and brominated lipid X in mixtures with DOPC to Eq. 2. The mole fraction of cardiolipin was calculated on a chain basis, to account for the fact that cardiolipin contains four fatty acyl chains compared to two chains in phosphatidylcholine.