Detecting Electrical Conductance of PilV in Bulk Solution Using MCBJ

Minor pilins are the first type IV pili (T4P) proteins known to interact with electroactive surfaces, acting as an anode in electron transfer. In this study, we used the mechanically controlled break-junction (MCBJ) technique to measure the electrical conductance in bulk solution of the minor pilin PilV from the acidophile Acidithiobacillus thiooxidans and a lysozyme. Conductance was assessed at two different concentrations and at room temperature, with molecules lacking binding-specific ligands. The signal appeared after the final step of the contact-breakage process of the electrodes. We propose that this signal corresponds to multiple PilV or lysozyme molecules forming a transient junction between the metal contacts, lasting for microseconds. Our findings provide in situ evidence that PilV may contribute to T4P and biofilm conductivity in A. thiooxidans. Additionally, we demonstrate that the MCBJ technique enables real-time conductance detection of molecules in bulk solution.