FIGURE 1.

Ca²⁺ binding activity of Xenopus dicalcin. A, ⁴⁵Ca blot of Xenopus dicalcin. Recombinant dicalcin and molecular size markers (∼6 μg each) were electrophoresed and transferred onto a PVDF membrane. Blots of recombinant Xenopus dicalcin and size markers were soaked in Tris-buffered saline containing 1 mm ⁴⁵CaCl₂. After washing, the membrane was dried, and bound ⁴⁵Ca was detected. CBB, Coomassie brilliant blue staining; ⁴⁵Ca, ⁴⁵Ca blot; Marker, molecular size markers; Dicalcin, recombinant Xenopus dicalcin. B, Ca²⁺ binding to Xenopus dicalcin. Recombinant dicalcin (final concentration, 10 μm) was incubated with various concentrations of ⁴⁵CaCl₂. The graph shows the amount of Ca²⁺ bound to Xenopus dicalcin as a function of free Ca²⁺ concentration (n = 6, mean ± S.D.). The data were fitted by a Hill equation (solid line).