Table 1.
Single-channel conductance and critical voltage of various OmpF mutants
| Mutation | Λ, nS (n) | Vc, mV (m) |
|---|---|---|
| Wild-type | ||
| OmpF | 0.84 ± 0.06 (156) | 145 ± 7 (10) |
| On barrel wall | ||
| S272A | 0.76 ± 0.02 (173) | 196 ± 13 (15) |
| E296L | 0.66 ± 0.04 (87) | 202 ± 11 (17) |
| E296A | 0.78 ± 0.03 (67) | 172 ± 12 (14) |
| E296Q | 0.78 ± 0.03 (63) | 147 ± 10 (19) |
| D312N | 0.60 ± 0.03 (137) | 215 ± 15 (12) |
| A333C | 0.81 ± 0.03 (50) | 182 ± 17 (17) |
| On L3 | ||
| E117C | 0.68 ± 0.02 (97) | 199 ± 12 (15) |
| Δ116–120 | 0.17 ± 0.03 (90) | 217 ± 14 (18) |
| L3 tethered to barrel wall | ||
| E117C/A333C | 0.71 ± 0.02 (159) | 191 ± 12 (14) |
| Same, reduced | 0.57 ± 0.01 (52) | 198 ± 7 (8) |
Values of the conductances (Λ), and those for the critical threshold voltages (Vc) are given with standard deviations. The number of events for the determinations of channel conductance is given in parentheses (n), and the number of experiments for the evaluation of Vc (over a voltage range of 0–230 mV) is also indicated in parentheses (m). For the determination of channel conductance, membranes with 5–7 trimers inserted were used. For the quantification of Vc, the number of trimers inserted into membranes was in the range of 15–20. For the double-Cys mutant, the channel properties were also determined by incubating the protein in 1 mM DTT for 10 min at room temperature prior to its incorporation into the planar bilayer. In these cases, DTT was present also in both compartments of the bilayer apparatus. Channel conductance was measured in 1 M NaCl/10 mM Tris⋅HCl/1 mM CaCl2, final pH 7.4.