FIGURE 7.
δ-Values (▪) for control and all asymmetric experimental cis/trans [KCl] conditions. The fraction of the Vj field (δ) sensed by spermine (z = +4) at the inhibitory site increased with elevations in the cis/trans K+ activity ratio with a Hill coefficient of 0.99 ± 0.16, indicative of a direct single-site interaction (see Supplementary Material, Fig. S5 for further details). The δ-value under symmetrically reduced [KCl] conditions (□) was less than that observed during the trans-only reduction. The shift in the δ-value from the low trans condition to the equivalent low cis-trans condition is indicated by the dashed arrow.