Figure 7.

Functional consequences of COOH-terminal deletions. (A) Representative single-channel traces from full-length KcsA and chymotrypsin-truncated KcsA (Δ125) from reconstituted proteoliposomes. Stationary recordings were obtained at 80 mV in symmetric 200 mM K⁺, pH 4.0, and were filtered at 2 kHz. Calibration scales are 10 pA and 250 ms. (B) Single-channel I-V curves calculated for control (•) and Δ125 (○) channels. Single-channel conductances calculated from the slope around 0 mV are 100 and 102 pS. (C) Effect of progressive COOH-terminal deletions on the pH dependence of ⁸⁶Rb⁺ influx. Error bars represent the SD and correspond to three to nine experiments. Individual curves were fitted to the Hill equation and the corresponding parameters for each truncation construct (apparent pKa and Hill coefficient, n) are plotted as a bar graph (right).