FIGURE 3.

The P, β, and T domains are needed for sensitivity to mambalgin-2. A–D, representative current traces generated by ASIC1a and ASIC1a/2a chimeras and evoked by pH 5.0 pulses of 30 s made at 1-min intervals from a holding pH of 7.4 (holding potential, −50 mV). Mambalgin-2 (Mamb-2) (400 nm) was applied for 30 s before the pH pulse. Three pulses before toxin application and two pulses after washing are shown for consistency. The red dashed line represents the current rundown, and a schematic illustrating the domain in ASIC1a that was swapped is shown beside the current trace for each chimera. E, bar graph representing the effects shown in A–D expressed as a percentage of the control current without toxin. The number of oocytes analyzed is shown within each histogram. Error bars represent S.E. Statistical comparison is with ASIC1a. F, mapping on the three-dimensional model structure of the ASIC1a·mambalgin-2 complex of residues in domain T that were mutated and are putatively involved in the interaction with mambalgin-2 (toxin shown in ribbon representation). Note that Val-352 cannot be displayed because it points toward the interior of the channel. G, bar graph representing the effect of mambalgin-2 (200 and 400 nm) on the different ASIC1a point mutants shown in F. The number of oocytes analyzed is indicated within each histogram. Data are means ± S.E. (error bars). Statistical comparison is with ASIC1a unless specified.