TABLE 1.
Dissociation constants (Kd) of 0.19 μm YtfQ for different sugars investigated by tryptophan fluorescence spectroscopy
The following compounds showed no change in fluorescence suggesting that they do not bind to the SBP: 1-phosphoglucose, 2-deoxyglucose, 6-phosphoglucose, altrose, fructose, glucosamine, glucuronate, lactose, lyxose, mannose, and sucrose. All titrations were performed at least three times. Standard deviations are reported to two significant figures.
| Ligand class | Ligand | Kd | S.D. |
|---|---|---|---|
| μm | μm | ||
| Hexose | Galactose | 1.7 | 0.30 |
| Talose | 25.7 | 2.5 | |
| Allose | 30.3 | 4.4 | |
| Glucose | NBa | ||
| Pentose | Arabinose | 1.3 | 0.24 |
| Ribose | 49.0 | 13 | |
| Other | Fucose (6-deoxy-l-galactose) | 6.2 | 0.54 |
| Methyl-β-galactoside | 145.4 | 21 | |
| Galacturonate | 220.9 | 22 |
a NB, no binding detected due to no apparent change in fluorescence upon addition of ligand.