TABLE II

Single-Channel Properties of A713X Homomeric Channels

γ1γ2γ21<γ>Poτoτc
pSpSpSmsms
A713wtND31 ± 1 (12)NDND0.034 ± 0.017 (12)0.9 ± 0.3 (7)125 ± 62 (4)
A713GND36 ± 2 (7)NDND0.014 ± 0.009 (7)1.2 ± 0.3 (6)208 (2)
A713C28 ± 2 (6)36 ± 2 (16)1.4 ± 0.1 (6)35 ± 4 (5)0.29 ± 0.08 (16)40 ± 20 (8)35 ± 15 (6)
A713T27 ± 4 (3)38 (2)1.2 (2)37 (2)0.36 ± 0.27 (3)144 ± 72 (3)9.3 (1)
A713D41 ± 2 (4)50 ± 2 (4)1.22 ± 0.03 (4)48 ± 2 (4)0.76 ± 0.05 (4)109 ± 47 (3)21 (1)
A713V17 ± 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, Po, 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 Po. 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: (P1γ1 + P2γ2)/(P1 + P2). Single-channel conductance and Po 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.