FIGURE 3.
Extension of the stretched kinetic model of prestin activity to provide salicylate competition with chloride. Xsal state is bound by salicylate. Xo state is unbound by anion. Xc state is bound by chloride, but intrinsic voltage sensor charge is not responsive to membrane electric field. Slow, multiexponential conformational transition to Xd state via Xn states enables voltage sensing of electric field. The αn and βn transitions are multiexponential (see “Experimental Procedures”). Depolarization moves positive sensor charge outward, simultaneously resulting in compact state C, which corresponds to cell contraction. Equivalence of αn and βn transition rate constants assures detailed balance of the reaction scheme.