TABLE 1

Voltage dependence of activation for WT and mutant mHCN2 channel currents

H397A, L399A, I401A, S420A, and G424A channels did not functionally express, as confirmed by insensitivity of oocyte currents to 20 mM CsCl.

Channel V1/2k min-Pon τact fast τact slowAf/(Af + As) τdeactn
mV ms ms
WT mHCN2 -74 ± 1.3 7.7 ± 0.5 0.04 ± 0.01 10 433 ± 57 2100 ± 231 0.62 ± 0.04 140 ± 5 5
Pore helix mutations
    M398A -96 ± 2.6 10.3 ± 1.2 0.52 ± 0.04 6 770 ± 64 394 ± 48 8
    L399V -87 ± 1.4 5.9 ± 0.2 0.14 ± 0.02 6 957 ± 73 7230 ± 911 0.72 ± 0.04 97 ± 5 4
    C400A -99 ± 1.5 9.8 ± 0.9 0.04 ± 0.01 6 571 ± 31 5300 ± 540 0.62 ± 0.04 63 ± 2 5
S6 domain mutations
    M421A -109 ± 1.5 12.7 ± 1.8 0.27 ± 0.03 8 2050 ± 220 1020 ± 74 8
    I422A -65 ± 2 10.4 ± 0.6 0.23 ± 0.03 4 536 ± 16 2500 ± 357 0.52 ± 0.02 780 ± 35 4
    V423A -97 ± 1.6 7.4 ± 0.6 0.11 ± 0.01 5 857 ± 102 68 ± 8 6
    A425G -72 ± 0.9 7.6 ± 0.4 0.12 ± 0.01 15 541 ± 28 2200 ± 184 0.75 ± 0.04 296 ± 12 15
    T426A -90 ± 0.4 5.1 ± 0.3 0.05 ± 0.01 5 313 ± 38 1670 ± 92 0.17 ± 0.04 34 ± 3 5
    C427A -80 ± 2.1 7.4 ± 0.5 0.16 ± 0.03 4 155 ± 48 845 ± 118 0.90 ± 0.04 128 ± 17 4
    Y428A -88 ± 0.9 5.8 ± 0.7 0.02 ± 0.01 5 958 ± 50 3220 ± 211 0.74 ± 0.02 48 ± 5 5
    A429V -115 ± 1.8 10.1 ± 1.1 0.09 ± 0.01 5 4770 ± 311 67 ± 11 4
    M430A -101 ± 1.7 6.4 ± 0.8 0.16 ± 0.01 7 3440 ± 56 70 ± 6 4
    F431A -92 ± 0.8 11.7 ± 0.5 0.10 ± 0.01 7 1660 ± 108 3390 ± 95 4
    I432A -85 ± 0.8 10.3 ± 0.5 0.68 ± 0.02 12 148 ± 11 4270 ± 419 0.67 ± 0.04 102 ± 8 8
    I432A/A425G -80 ± 1.6 12 ± 1.0 0.54 ± 0.02 11 60 ± 1.5 302 ± 29 0.52 ± 0.02 78 ± 3 9
    G433A -94 ± 0.9 10.1 ± 0.6 0.04 ± 0.01 8 270 ± 23 1250 ± 122 0.55 ± 0.04 125 ± 16 4
    H434A -89 ± 4.4 10.3 ± 0.6 0.08 ± 0.01 4 286 ± 23 1060 ± 96 0.64 ± 0.06 90 ± 6 5
    A435V -105 ± 0.5 9.9 ± 0.6 0.12 ± 0.01 6 1170 ± 137 78 ± 7 6
    T436A -97 ± 1.0 8.8 ± 0.7 0.10 ± 0.02 6 735 ± 74 55 ± 3 5
    A437V -96 ± 4 6.9 ± 0.9 0.08 ± 0.03 5 1160 ± 137 63 ± 3 4
    L438A -74 ± 2.4 17.1 ± 1.6 0.38 ± 0.04 4 233 ± 25 2180 ± 256 0.57 ± 0.05 292 ± 14 4
    I439A -77 ± 1.2 7.3 ± 0.6 0.19 ± 0.01 5 210 ± 38 474 ± 70 0.58 ± 0.04 54 ± 1 4
    Q440A -77 ± 1.6 8.6 ± 0.2 0.15 ± 0.02 7 268 ± 24 794 ± 179 0.53 ± 0.05 175 ± 10 4
  • V1/2, voltage required for half-maximal current activation; k, slope factor of the activation curve; min-Po, minimal open probability; τact, time constant for current activation (single exponential fit); τact fast and tact slow, time constants for fast and slow components of activation (two exponential fit); Af/(Af + As), relative amplitude of fast component of current activation (two exponential fit); τdeact, time constant for current deactivation at + 20 mV.