Fig. 5.

Mutational effects of loop-residues on the K_int and k_cat values of the Ca²⁺/Ca²⁺ exchange. (A) Mutational effects on the K_int and k_cat values of the Ca²⁺/Ca²⁺ exchange were analyzed as described in Fig. 4 (see also Materials and Methods). Data were derived from at least 3 independent experiments and are presented as mean ± SE. Mutations exhibiting K_int < < 1, K_int ≈ 1 and K_int > > 1 are in green, blue, and red, respectively. (B) Cartoon presentation of NCX_Mj. Mutated residues are shown as spheres, where the colored residues are assorted according to their mutational effects, as indicated in panel A. (C) The measured values of K_m^Cyt (blue bars) and K_m^Ext (red bars) of the Ca⁺/Ca²⁺ exchange reaction were derived from at least 3 independent experiments. Data are presented as mean ± SE. Residues are colored according to their mutational effects on K_int, as colored in panel A.