Single-channel analysis of recombinant C. trachomatis MOMP from BL21omp8 cells. A. Channel currents in response to two transmembrane voltage ramps (-100 mV to +100 mV), with 1 M KCl cis and trans. Up to 3 channels are open during ramp (a), and 2 of the channels close in succession at about +80 mV. In ramp (b), 1 channel is open at 0 mV, and 2 channels are open at +100 mV. B. Channel currents in the presence of 500 mM KCl cis and trans during two voltage ramps (as in A). Note the reduction in single-current amplitudes, and current reversal at 0 mV as in A. C. Currents during two voltage ramps in asymmetric KCl, 500 mM cis vs 50 mM trans. Note the shift in equilibrium potential (Er) from 0 mV to -30 mV (arrowed). Positive (upgoing) currents at 0 mV indicate a net flux of K+ cis to trans in the absence of an electrical driving force. D. Equilibrium currents in symmetric 500 mM KCl at a constant holding potential of +100 mV, showing brief single-channel closures and voltage-dependent inactivation of all 3 channels within 5 s.