Little is known about how conformation changes of proteins control biological function. How do the locations reveal themselves as measurable physical properties of the protein?One place these questions can be (mostly) answered is in the proteins that form the voltage activated channels of nerve.
We calculate conformation currentin Na Vand K V channels in response to a step of voltage. Changing isoleucine of K V channels to threonine of Na V channels speeds responses to voltage, andallows the separation of opening of Na V and K V channels needed to create nerve signals.
The polarization mechanism we propose is both logically sufficient and logically necessary to account for the difference in speed and the structural movements of voltage sensors. It is sufficient because we reproduce properties of gating current under a realistic range of conditions.It is necessary because the movement of chargeswe calculate must produce the currents we calculate given the universal and exact nature of the Maxwell equations that link charge and current. Our conclusions arise fromthe universal and exact conservation of total current implied by the Maxwell equations.
Of course, evolution is not logical. It often provides redundant mechanismsbeyond the necessary and sufficient. These mechanisms may provide properties not glimpsed here. These mechanisms may also control the speed of gating and give the gating system biologically and evolutionarily useful properties unknown to us.