Sensing Multivalent Ions with Lysenin Channels
Lysenin, a Pore Forming Toxin extracted from the earthworm E. foetida, inserts uniform and large conductance channels into planar Bilayer Lipid Membranes containing sphingomyelin. Our experiments reveals that the macroscopic currents through lysenin channels biased by negative voltages strongly decrease when small amounts of multivalent cations are added to the bulk electrolyte. The changes in conductance are reversible and the removal of multivalent ions by chelation or precipitation restores the initial conductance. Preliminary experiments indicate that the mechanism responsible for the observed decrease in conductance is channel’s gating induced by multivalent ions. Divalent metals preferentially induce channels' transition to sub-conducting states, while trivalent metals induce full closing. Our experimentation with voluminous organic cations indicates that both effective charge and size of the added cations influences the changes in channel’s conductance. Such findings open new avenues in our understanding on ion channels’ ligand-induced gating and in developing highly-sensitive sensors for multivalent ions.