Biophysical properties of heteromeric currents from oocytes coexpressing Kv2.1:Kv6.4-PIPIIV-Kv2.1CT. (A) Example currents recorded from an oocyte expressing Kv2.1:Kv6.4-PIPIIV-Kv2.1CT in a 1:10 ratio in response to 1-s voltage steps ranging from −80 to +40 mV in 20-mV increments from a holding potential of −100 mV. The voltage protocol is shown below the currents, the 0-mV trace is highlighted in magenta, and scale bars are given for time and current amplitude. (B) Normalized GV relationship for Kv2.1+Kv6.4-PIPIIV-Kv2.1CT determined from isochronal tail currents recorded at −50 mV after 1-s steps to the indicated voltages. Data points show mean ± SEM (n = 10), and the solid blue curve represents a single Boltzmann distribution fit of the data (V₅₀ and slope are included in Table 1). Dashed magenta and black curves show the Boltzmann fits for Kv2.1 homomers and Kv2.1:Kv6.4 WT, respectively. (C) Example current traces for the SSI protocol for an oocyte expressing Kv2.1:Kv6.4-PIPIIV-Kv2.1CT in a 1:10 cRNA ratio. The voltage protocol is indicated below the current, the oocyte was held at −100 mV and current traces recorded in response to 4-s prepulses ranging from −120 to −40 mV in 20-mV increments are shown, and the −40 mV trace is highlighted in magenta. Pre-pulses were followed by a 500-ms step to +40 mV to show current availability. (D) Normalized SSI relationship determined for Kv2.1:Kv6.4-PIPIIV-Kv2.1CT from peak current amplitudes recorded at +40 mV following 4-s prepulses to the indicated voltages. Data show mean ± SEM (n = 10), the blue curve represents a single Boltzmann fit (parameters in Table 1), and the dashed magenta and black curves show Boltzmann fits for Kv2.1 and Kv2.1:Kv6.4 WT, respectively.