Fig. 5.

CaM1 could bind to the NT and CT peptides of L-VGCC. a Schematic drawing of peptide fragments of L-VGCC. Eight peptides derived from the intracellular regions of the channel, including CT and NT peptides, were constructed as GST-fusion peptides. The CT domain was divided into three parts, as illustrated. CT1 contained regulatory regions (shown as boxes), a Ca²⁺-binding EF-hand motif (EF), and two CaM-binding domains (PreIQ and IQ). Fragments of CT1 (i.e., CT1A, CT1B, PreIQ, and IQ) were also prepared. b Amino acid sequence deduced from the EF-hand, PreIQ and IQ domains. c, d GST pull-down assay for CaM binding under 1 mM Ca²⁺. GST-fusion peptides (0.35 μM) were mixed with 0.35 μM CaM1, and bound CaM1 was separated by SDS-PAGE. Two micrograms of BSA (66 kDa) and 2 μg of CaM1 (19 kDa) were run as standards. e-h Concentration-dependent binding of CaM1 to CT1 (△), CT1B (□), IQ (○), PreIQ (◊), and the NT region (☆) under 1 mM Ca²⁺ (e, f) and 100 nM Ca²⁺ (g, h). The data are shown as the mean ± SD from six independent experiments. ****p < 0.0001. ns, not significant.