Fig. 6.

Spatial distribution of residues differentially affecting the V_max and K_int values. (A) For each mutant, the V_max value of the Ca²⁺/Ca²⁺ exchange was plotted vs. its position within the pore. The residue-positions are expressed as the distance from the pore center (the “zero” represents the position of the pore center). The residues significantly affecting the V_max value (< 20% of WT V_max) are shown in blue, where less significant residues affecting the ion-transport rates are shown as solid black circles. The solid and dashed blue circles represent the ion-coordinating and non-coordinating residues, respectively. (B) Topological presentation of mutated positions. The mutational effects of residues on V_max are colored as in panel A. (C) For each mutant, the K_int value was plotted vs its distance from the pore center. The mutants exhibiting high K_int values are indicated in blue, whereas the solid and dashed circles represent the pore-forming and helix-loop residues, respectively. Solid black cycles represent mutations having an insignificant effect on K_it (D). Topological presentation of mutated positions are colored as in panel C.