FIGURE 6.
CTP1 displays ion channel-like activity in planar lipid bilayers. A, traces of currents from two representative experiments attempting incorporation of the CTP1 (top) and CTP1-L210A,F211A (bottom) peptides into the artificial lipid bilayers. The peptide-concentration increments are indicated by arrows. Breaks within traces correspond to 1-min cis chamber solution stirring intervals after peptide additions. B, higher resolution (4-s long) fragments of the CTP1-generated currents at the time points corresponded to the numbered circles in A. C, current sublevel-probability histograms obtained from continuous 60-s long fragments of traces presented in A during the first minute of the channel activity appearance for CTP1 (40 μm) and during prolonged incubation with CTP1-L210A,F211A (50 μm). D, values of the mean current (Imean ± S.E.) calculated from 60-s long recordings and averaged for four experiments for each peptide. For CTP1, the 60-s recordings were taken immediately after appearance of the initial series of spikes indicating formation of the CTP1-assembled channels (*, p < 0.05). E, representative 4-s long recordings obtained at various membrane potentials (shown on the right) from the same planar lipid bilayer within an interval of quasistable basal current carried by CTP1-induced (40 μm) ion channels in asymmetric bilayer ionic conditions (cis, HEPES/Tris; trans, HEPES/Ba2+, 50 mm, see ”Experimental Procedures“).