TABLE 2.
Dissociation constants (Kd) of siderophore-55Fe to outer membrane transporters FptA and FetA determined in vivo at 0 °C PAD07 (expressing FptA) and CHA1085 (expressing FetA) cells were prepared as described under “Experimental Procedures” and were incubated with a series of concentrations of 55Fe-Pch or 55Fe-EPch for 1 h at 0 °C. The mixtures were centrifuged, and the radioactivity in the pellet was counted. The constants were determined from a Scatchard representation, and the errors were determined from multiple Scatchard plots.
|
Siderophores
|
Outer membrane transporters
|
|
|---|---|---|
| FptA | FetA | |
| 55Fe-Pch | Kd = 2.5 nm ± 1.1 | No binding observed |
| 55Fe-NeoPch | Kd = 29 nm ± 11 | No binding observed |
| 55Fe-EPch | No binding observed | Kd = 3.7 nm ± 2.1 |