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In the Ca2+-free form of CaM and TnC, the two helices of the EF-hand are close together; this arrangement has been termed the 'closed conformation'. All EF-hands in the two proteins (blue) exhibit similar helix positions, and all undergo a similar conformational change upon binding Ca2+. EF-hands of CaM and TnC in the calcium-loaded forms (red, orange) are in the 'open conformation', in which the helices are nearly perpendicular to each other. The conformational changes in CaM and N-TnC lead to an exposure of a hydrophobic surface with which CaM binds its targets and TnC binds to TnI. |
| EF-hand (helix residues) | N-terminal coordinate
of second helix |
theta | phi | omega |
| apo-CaM EF1 (12-19, 29-39) | (10.573, 0.000, -3.582) | 44.694 | 123.707 | 105 |
| apo-CaM EF2 (48-55, 65-75) | (11.621, 4.695, -0.666) | 39.692 | 137.273 | 98 |
| apo-CaM EF3 (85-92, 102-112) | (10.112, 0.000, -1.818) | 37.629 | 106.569 | 127 |
| apo-CaM EF4 (121-128, 138-148) | (10.903, 2.318, -2.377) | 49.428 | 104.832 | 183 |
| Ca2+-CaM EF1 (12-19, 29-39) | (5.796, -0.815, -8.909) | 86.587 | 106.444 | 67 |
| Ca2+-CaM EF2 (48-55, 65-75) | (8.487, -1.193, -6.963) | 92.220 | 101.984 | 98 |
| Ca2+-CaM EF3 (85-92, 102-112) | (7.023, 0.000, -8.359) | 75.449 | 101.425 | 87 |
| Ca2+-CaM EF4 (121-128, 138-148) | (8.919, -0.780, -6.032) | 62.856 | 111.203 | 76 |
| EF-hand (helix residues) | N-terminal coordinate
of second helix |
theta | phi | omega |
| apo-TnC EF1 (22-29, 39-49) | (10.292, -1.264, -3.444) | 35.382 | 102.549 | 122 |
| apo-TnC EF2 (58-65, 75-85) | (9.709, 6.305, -2.133) | 33.276 | 128.563 | 90 |
| Ca2+-TnC EF1 (22-29, 39-49) | (6.871, -0.360, -8.632) | 77.512 | 93.203 | 89 |
| Ca2+-TnC EF2 (58-65, 75-85) | (8.902, -1.251, -5.947) | 93.272 | 104.486 | 79 |
| Ca2+-TnC EF3 (98-105, 115-125) | (8.227, -0.575, -8.154) | 73.815 | 88.186 | 106 |
| Ca2+-TnC EF4 (134-141, 151-161) | (9.190, 0.000, -6.282) | 82.540 | 106.503 | 114 |
NB: values obtained using apo-CaM EF1 (as in refcam.pdb) as the reference EF-hand.