FIGURE 10.

The α-spectrin EF-domain binds calmodulin. A, ¹²⁵I-labeled CaM binding to GST-α18–21EF (0.76 μm) ± Ca²⁺ (1.5 mm) is shown. The incubation volume was 200 μl. B, ¹²⁵I-labeled α18–21EF (4.2 μm) binding to CaM-Sepharose (10 μl, diluted 1:1 with HEPES binding buffer) with increasing free Ca²⁺. ¹²⁵I-Labeled α18–21EF binding to Sepharose without CaM with increasing calcium was used as the background binding and was subtracted at each point.