TABLE II.
Single-Channel Properties of A713X Homomeric Channels
| γ1 | γ2 | γ2/γ1 | <γ> | P o | τo | τc | |
|---|---|---|---|---|---|---|---|
| pS | pS | pS | ms | ms | |||
| A713wt | ND | 31 ± 1 (12) | ND | ND | 0.034 ± 0.017 (12) | 0.9 ± 0.3 (7) | 125 ± 62 (4) |
| A713G | ND | 36 ± 2 (7) | ND | ND | 0.014 ± 0.009 (7) | 1.2 ± 0.3 (6) | 208 (2) |
| A713C | 28 ± 2 (6) | 36 ± 2 (16) | 1.4 ± 0.1 (6) | 35 ± 4 (5) | 0.29 ± 0.08 (16) | 40 ± 20 (8) | 35 ± 15 (6) |
| A713T | 27 ± 4 (3) | 38 (2) | 1.2 (2) | 37 (2) | 0.36 ± 0.27 (3) | 144 ± 72 (3) | 9.3 (1) |
| A713D | 41 ± 2 (4) | 50 ± 2 (4) | 1.22 ± 0.03 (4) | 48 ± 2 (4) | 0.76 ± 0.05 (4) | 109 ± 47 (3) | 21 (1) |
| A713V | 17 ± 6 (3) | 35 ± 4 (6) | 2.4 ± 1 (3) | 23 ± 6 (3) | 0.53 ± 0.17 (6) | 69 ± 31 (5) | 59 ± 21 (4) |
Properties of A713X channels measured in outside-out patches from Xenopus oocytes. Values are mean ± SEM (n = number of patches). For each isoform, a subset of the collected patches were used for each calculation. Only patches with one to two channels were used to measure γ, P o, and τo. Only patches where no double openings were observed were used to calculate τc. γ1 and γ2 represent the smaller and larger subconductance state, respectively. For two-channel patches, the square root of the probability of not being closed was used as an estimate of P o. In cases in which channels lacked substates, the conductance was considered to represent the substate with the closest conductance. <γ> represents weighted average conductance calculated according to the relative occupancy of γ1 and γ2: (P 1γ1 + P 2γ2)/(P 1 + P 2). Single-channel conductance and P o were calculated from all-points histograms, which were derived from recordings that were a total of 68.0, 9.4, 91.5, 40.5, 40.4, 23.4 min long for A713wt, A713G, A713C, A713T, A713D, A713V, respectively. Dwell times were derived from recordings containing a total of 69.2, 103.6, 106.8, 17.5, 13.0, 14.0 thousand events for A713wt, A713G, A713C, A713T, A713D, A713V, respectively.