Figure 3.
Stretched kinetic model of prestin activity within the plasma membrane. Xo state is unbound by anion. Xc state is bound by anion but intrinsic voltage sensor charge is not responsive to membrane electric field. Slow, multi-exponential conformational transition to Xd state via Xn state enables voltage sensing of electric field. Depolarization moves positive sensor charge outward, simultaneously resulting in compact state C, which corresponds to cell contraction. Equivalence of αn and βn transition rates assures detailed balance of the reaction scheme. To see this figure in color, go online.