FIGURE 9.

Ca²⁺ and calmodulin regulate binding of protein 4.2 to the α-spectrin EF-domain. A, ³⁵S-labeled protein 4.2 binding to GST-α18–21EF (0.4 μm) as a function of Ca²⁺ concentration in the presence or absence of calmodulin (5 μm) is shown. B, binding of the ¹²⁵I-labeled G₃ peptide of protein 4.2 (13.5 μm) to GST-α18–21EF (0.76 μm) as a function of Ca²⁺ concentration in the presence or absence of calmodulin (5 μm) is shown.