Table 2.
Effect of sugar binding on sm-FRET parameters
| Location of double-labeled Cys pairs | LacY | No sugar |
NPG (1 mM) |
NPGlc (1 mM) |
NPG-induced distance change, Å | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| E* | E† | Distance, Ň | E* | E | Distance, Å | E* | E | Distance, Å | |||
| Cytoplasmic side | Wild type | 0.536 (±0.013) | 0.468 (±0.013) | 51.5 | 0.584 (±0.009) | 0.523 (±0.009) | 49.7 | 0.547 (±0.001) | 0.480 (±0.001) | 51.1 | 1.4–1.8 decrease |
| 73/401 | 154G | 0.512 (±0.007) | 0.444 (±0.008) | 53.1 | 0.611 (±0.007) | 0.552 (±0.009) | 49.5 | 0.523 (±0.026) | 0.456 (±0.030) | 52.7 | 3.2–3.6 decrease |
| Periplasmic side | Wild type | 0.416 (±0.004) | 0.342 (±0.003) | 56.8 | 0.344 (±0.004) | 0.264 (±0.004) | 60.4 | 0.411 (±0.010) | 0.336 (±0.011) | 57.0 | 3.4–3.6 increase |
| 164/375 | 154G | 0.360 (±0.001) | 0.282 (±0.001) | 57.8 | 0.363 (±0.010) | 0.283 (±0.008) | 57.8 | 0.359 (±0.001) | 0.279 (±0.002) | 57.9 | No significant change |
†E is a corrected sm-FRET efficiency (23).
‡Distances have a precision of ±1 Å.