Figure 3. Single-channel recordings and analysis of conductance of purified MspA and MspA-MspB₁₇ dimer in lipid bilayer.

Single-channel recordings of purified wt MspA (A) and MspA-MspB₁₇ dimer (C) in a diphytanoyl phosphatidylcholine (DphPC) membrane in the presence of approximately 100 ng/mL protein sample. Protein solutions were added to both sides of the membrane and data were collected from at least five different membranes. −10 mV transmembrane potential was applied and current was measured in 1 M KCl solution, pH 7.0 Analysis of single-channel conductances of wtMspA (B) and MspA-MspB₁₇ dimer (D). To avoid possible contamination of the MspA-MspB₁₇ preparation with MspB, the subunit dimer protein was excised from the gel and electro-eluted. Analysis of the probability P of a conductance step G for single-channel events. The average single-channel conductances were 4.8 nS, and 2.2 nS for wt MspA, and MspA-MspB₁₇ dimer, respectively.