TABLE 3.
Annular and non-annular binding constants for KcsA
| Binding constant
|
||||
|---|---|---|---|---|
| Non-annular binding constant (mole fraction−1)
|
||||
| Lipid | KCl (mM) | Annular binding constant (relative to DOPC) | Model 1 | Model 2 |
| Phosphatidylserine | 0 | 0.83 ± 0.16 | 2.53 ± 0.32 | 5.71 ± 1.11 |
| 500 | 1.27 ± 0.22 | 0.26 ± 0.25 | 0.49 ± 0.48 | |
| Phosphatidic acid | 0 | 1.38 ± 0.26 | 1.51 ± 0.62 | 3.39 ± 1.41 |
| 500 | 1.47 ± 0.36 | 0.48 ± 0.33 | 0.94 ± 0.64 | |
| Phosphatidylglycerol | 0 | 1.26 ± 0.06 | 0.66 ± 0.35 | 1.46 ± 0.73 |
| Cardiolipin | 0 | 0.41 ± 0.09 | 2.77 ± 0.67 | 7.65 ± 3.96 |
Annular lipid binding constants relative to DOPC were determined by fitting quenching data for KcsA in mixtures of BrPC and anionic lipid to Eq. 2. Non-annular binding constants were determined by fitting quenching data for KcsA in mixtures of DOPC and brominated anionic lipid to Eq. 5 (Model 1) or Eq. 6 (Model 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.