Abstract
Peptides of 12 amino acids were tethered via a terminal cysteine to monoβ, diβ, triβ, and tetrabromomethylβsubstituted benzene to produce bundles of one to four peptide strands (CY12βT1 to CY12βT4, respectively). The interaction of the bundles with the Ξ±βhemolysin pore was assessed by measuring the blockade currents (I) and times (T) at an applied potential of β 50, β 100, and β 150 mV. Three types of events could be distinguished: bumping events, with small I and short T where the molecule transiently interacts with the pore before diffusing away; translocation events, where the molecule threads through the pore with large I and the value of T decreases with increasing voltage; and intercalation events, where the molecule transiently enters the pore but does not translocate with large I and the value of T increases with increasing voltage. CY12βT1 and CY12βT2 gave only bumping and translocation events; CY12βT3 and CY12βT4 also gave intercalation events, some of which were of very long duration. The results suggest that three uncoiled peptide strands cannot simultaneously thread through the Ξ±βhemolysin pore and that proteins must completely unfold in order to translocate. Copyright Β© 2010 European Peptide Society and John Wiley & Sons, Ltd.