Partial recovery of the translocation rate of MTS-ES–reacted LF_N (red) when positively charged lysines are flanking the introduced SO₃⁻. The experiments were performed as described in Fig. 3. The rate of translocation of MTS-ACE–reacted LF_N E126C, T199C, and N242C (black) was the same as that of WT LF_N and the unreacted lysine mutants (not depicted). Note that one lysine adjacent to the SO₃⁻ (orange in E126C and N242C, and purple in T199C) increased the rate of translocation, and two lysines, one on either side of the SO₃⁻ (green in E126C), produced an even greater increase in the rate of translocation, although still considerably short of the rate of translocation of WT LF_N.