FIGURE 5.

Ca²⁺ sensitivity. A and B, representative SDS-PAGE of proteins used for in vitro assays. Lane M, molecular mass marker. A, purified human β-cardiac S1 from C2C12 cells, actin from chicken skeletal muscle, human α Tm from E. coli, and human Tn from E. coli. B, purified Tns and reconstitution of components into regulated thin filaments. C, DCM mutants D84N and D230N (blue) shift the pCa₅₀ of RTF-stimulated ATPase activity to the right relative to WT (black). D, HCM mutants (red) and predicted HCM mutant E181K (green) shift the pCa₅₀ to the left. E, DCM mutants D84N and D230N (blue) do not significantly change the ANS fluorescence response to Ca²⁺ relative to WT (black). F, all HCM mutants (except I172T) have increased changes in ANS fluorescence relative to WT. Values are in Tables 3 and 4. All graphs were best fit to mean ± S.E. from ≥3 experiments. The maximum S.E. for ATPase was 11 units and for ANS assay was 4 units of the y axis.