Protein electrostriction: a possibility of elastic deformation of the α-hemolysin channel by the applied field

Abstract

While conformational flexibility of proteins is widely recognized as one of their functionally crucial features and enjoys proper attention for this reason, their elastic properties are rarely discussed. In ion channel studies, where the voltage-induced or ligand-induced conformational transitions, gating, are the leading topic of research, the elastic structural deformation by the applied electric field has never been addressed at all. Here we examine elasticity using a model channel of known crystal structure-Staphylococcus aureus alpha-hemolysin. Working with single channels reconstituted into planar lipid bilayers, we first show that their ionic conductance is asymmetric with voltage even at the highest salt concentration used where the static charges in the channel interior are maximally shielded. Second, choosing 18-crown-6 as a molecular probe whose size is close to the size of the narrowest part of the alpha-hemolysin pore, we analyze the blockage of the channel by the crown/K(+) complex. Analysis of the blockage within the framework of the Woodhull model in its generalized form demonstrates that the model is able to correctly describe the crown effect only if the parameters of the model are considered to be voltage-dependent. Specifically, one has to include either a voltage-dependent barrier for crown release to the cis side of the channel or voltage-dependent interactions between the binding site and the crown. We suggest that the voltage sensitivity of both the ionic conductance of the channel seen at the highest salt concentration and its blockage by the crown reflects a field-induced deformation of the pore.

High-resolution experimental and computational electrophysiology reveals weak β-lactam binding events in the porin PorB

“…2D), which however can be attributed to factors beyond the actual binding site of ampicillin, e.g. elastic structural deformations caused by the applied electric field 45,46 .…”

Mechanism of KCl Enhancement in Detection of Nonionic Polymers by Nanopore Sensors

“…Bilayer lipid membranes of 40 pF capacitance were formed by the lipid monolayer apposition technique, using 1,2-diphytanoyl-sn-glycero-3-phosphocholine (Avanti Polar Lipids, Alabaster, AL) at 25 6 1°C, as described previously (29). The membrane-bathing aqueous solution contained 1 M to 4 M KCl in 5 mM Tris-citric acid buffer (pH 7.5).…”

High-resolution experimental and computational electrophysiology reveals weak β-lactam binding events in the porin PorB

“…2D), which however can be attributed to factors beyond the actual binding site of ampicillin, e.g. elastic structural deformations caused by the applied electric field 44,45 .…”