FIGURE 6.

NAD kinase affinity for CaM, sCaM1, and sCaM4. The CaM-dependent change in fluorescence for the intrinsic Trp in NADK is shown as a function of -log[CaM] for CaM (black), sCaM1 (red), and sCaM4 (blue). Increasing amounts of each WT protein were added to 2 mL of buffer (200 mM MOPS, 150 mM KCl, 2 mM EGTA, pH 7.0) containing 1 μM NADK with 100 μM Ca²⁺ (pCa = 4) at 20°C. There was no fluorescence change for any of the CaMs in the absence of Ca²⁺ (data not shown). Significant difference (p < 0.05) of sCaM1 and sCaM4 from CaM is denoted by (^∗). The free [Ca²⁺] was calculated as described in section “Materials and Methods.” All traces were fit and affinities calculated as described in section “Materials and Methods.”