The effect of introducing one SO₃⁻ (by reacting an LF_N cysteine mutant with MTS-ES) on the translocation rate of LF_N. The panels show the normalized rise of conductance (a reflection of translocation of LF_N through the (PA₆₃)₇ channel) that occurred when, after the perfusion of the indicated MTS-reacted LF_N cysteine mutant out of the cis compartment, the voltage was stepped from +20 to +55 mV. Note the very slow translocation of the MTS-ES–reacted LF_N (red). In contrast, the translocation rates of the MTS-ET–reacted (blue) and the MTS-ACE–reacted LF_N (black) were essentially the same as that of WT LF_N (which is not shown in the panels for clarity), with a half-time of ∼5 s.