FIGURE 2.

The C terminus acts as an autoinhibitory domain. A, schematic of the membrane topology of a single subunit of the SpIH channel. Representative currents were measured from inside-out excised patches of oocyte membrane. Voltage pulses were applied to patches in the range of −30 to −120 mV, followed by a voltage step to −40 mV. The holding voltage was 0 mV. Currents were measured in the absence of cyclic nucleotides (black traces) and in the presence of 1 mm cAMP (red traces). B, schematic representing the topology of the C-terminal deletion mutant (deleted amino acids 471–767). Representative currents were measured over a voltage range of −40 to −120 mV from a 0-mV holding potential in the absence of cyclic nucleotides.