Bioferroelectricity in models of voltage-dependent ion channels

Abstract

Ion channels are glycoprotein components of biomembranes that switch specific ionic currents on and off. It is here argued that, in the nonconducting phase, these macromolecules are ferroelectric liquid crystals, containing S4 and other segments that share the properties of chirality and tilt with SmC* phases. In the ion-conducting phase they are modeled as metalloproteins, with their structure coordinated by the permeant ions, which are dehydrated by enzymatic action as they enter the channel. Permeant ions may replace structural protons in an ion-exchange reaction. The conformational transition from closed to open phase is postulated to be a soft mode transition, in which the tilt angles of the S4 segments decrease to zero. It is also likely to involve the flexoelectric effect. Experimental data support these models.

Key Words:

• ion channels
• excitability
• ferroelectric liquid crystals
• superionic conduction
• metalloprotein
• S4 segments