Zipper transition in an alpha-helix: a mechanism for gating of voltage-sensitive ion channels in a biological membrane.

It is suggested that the gating currents which control the ion channels in a biological membrane are comprised of positive charges crossing the membrane along chains of hydrogen bonds. These chains are the sets of hydrogen bonds which hold alpha-helical protein segments in their rigid conformations. The passage of a positive charge in one direction along such a chain will convert hydrogen bonds from the usual rigid N--C = O...H--N form to a flaccid N = C--O--H...N form. This "zipper" transition can be reversed by the passage of the positive charge along the return route. A flaccid protein rod can clog an ion channel and thereby close it. When all of the protein rods framing an ion channel are in the rigid conformation, the channel is open. This mechanism is used to explain some of the observed characteristics of calcium ion channels and sodium ion channels.