FIGURE 3.

Long-lived subconducting states of MscL are voltage-dependent. (A) Representative fragments of a continuous MscL trace recorded under constant 207 mm Hg suction at −20 (bottom), −40 (middle), and −60 mV (top). (B) All-point amplitude histograms generated from 1-min fragments of the continuous trace recorded at a constant tension and three different voltages. The occupancies of the long-lived substates with the relative conductances of 0.78 and 0.64 increase at more negative membrane potentials. (C) Occupancies of the fully open state (open symbols) and the two long-lived substates L_0.78 (solid symbols) and L_0.64 (shaded symbols), normalized relative to the occupancy of the closed state. The solid lines represent the mean probability slopes for four independent data sets. The transferred net charges (q_ik) resulted from transitions between any two states i and k and were calculated from the ratios of probabilities by fitting with equation p_k/p_i = [p_k(0)/p_i(0)] × exp(−q_ik ΔV/kT), where p_i(0) and p_k(0) are the probabilities of specified states at 0 voltage. An outward movement of 0.8 e and inward movement of 3.5 e across the entire field were associated with C→O and O→L_0.78 transitions, respectively.