TABLE 2.
Comparison of helix orientations in EF-hand proteins
Interhelical angles are shown in degrees with interhelical distances shown in Å in parentheses. Calculations refer to the following structures. Ca-CaM is Ca2+ -loaded target-free calmodulin (PDB code 1EXR, 1.00 Å) (67), IQ-Ca-CaM is Ca2+ -loaded calmodulin bound to the voltage-gated Ca2+ channel Cav1.2 IQ-motif (PDB code 2F3Y, 1.45 Å) (81), and apoCaM is apoCa2+ target-free calmodulin (PDB code 1CFD, NMR) (82), with helix I defined as residues 6-18, helix II as residues 29-38, helix III as residues 45-54, and helix IV as residues 65-74. Interhelical angles for the Nav1.2 CTD are the averages with S.D. for the structural ensemble.
| Molecule | Helix II | Helix III | Helix IV |
|---|---|---|---|
| Helix I | |||
| Ca-CaM | 85 (20.4) | −134 (25.5) | 91 (14.6) |
| IQ-Ca-CaM | 92 (18.3) | −161 (21.9) | 117 (10.1) |
| ApoCaM | 136 (12.9) | −93 (21.2) | 126 (11.9) |
| Nav1.2 CTD | 152 ± 2 (10.9 ± 0.1) | −103 ± 6 (20.9 ± 0.3) | 143 ± 1 (15.7 ± 0.2) |
| Helix II | |||
| Ca-CaM | 83 (10.1) | −20 (16.7) | |
| IQ-Ca-CaM | 107 (11.2) | −41 (18.6) | |
| ApoCaM | 125 (11.9) | −49 (12.9) | |
| Nav1.2 CTD | 100 ± 5 (10.8 ± 0.4) | −46 ± 2 (13.4 ± 0.1) | |
| Helix III | |||
| Ca-CaM | 65 (15.3) | ||
| IQ-Ca-CaM | 80 (16.5) | ||
| ApoCaM | 129 (14.1) | ||
| Nav1.2 CTD | 98 ± 6 (14.4 ± 0.4) |