FIGURE 5.

Calcium binding to RmRec/dRec. 40 μM RmRec (open circles) or 20 μM dRec (open squares) were incubated with increasing Ca²⁺ concentrations in the presence of ⁴⁵Ca²⁺ and the Ca²⁺-bound protein was separated by ultrafiltration. Stoichiometry of Ca²⁺ binding determined from the excess Ca²⁺ in the protein sample over that present in the ultrafiltrate was plotted versus [Ca²⁺]_free and the plots were fitted to the 4-parameter Hill equation. Solid and dashed curves represent the best fits for RmRec and dRec, respectively.