|
Domain VI of calpain contains five EF-hands, of which EF1, EF2 and EF3 bind Ca2+, but in doing so undergo little conformational change. (EF1, the green-cyan clinder pair at right, is likely positioned unusually and exhibits larger conformational change due to the longer linker between EF1 and EF2.) The structure of EF4 is also well conserved (green-cyan cylinder pair at far left) but is unusually positioned, possibly due to its role of stabilising the EF1-EF2 and EF3-EF4 pairs. EF5 is essential to dimer formation (pairing with EF5 of the homodimer observed in solution, and probably in the heterodimer with domain IV) and Ca2+ activation of calpain. |
| EF-hand (helix residues) | N-terminal coordinate
of second helix |
theta | phi | omega |
| apo-calpain EF1 (100-107, 119-129) | (5.517, 10.828, -4.996) | 39.993 | 152.552 | 70 |
| apo-calpain EF2 (146-153, 163-173) | (9.860, 0.863, -3.317) | 57.573 | 97.310 | 114 |
| apo-calpain EF3 (176-183, 193-203) | (9.689, 1.535, -4.651) | 28.489 | 117.287 | 103 |
| apo-calpain EF4 (211-218, 228-238) | (1.751, -9.930, -6.511) | 44.178 | 8.959 | 203 |
| apo-calpain EF5 (241-248, 260-270) | (10.988, 7.136, -0.091) | 25.602 | 162.685 | 123 |
| Ca2+-calpain EF1 (100-107, 119-129) | (3.747, 8.415, -11.462) | 56.542 | 141.515 | 47 |
| Ca2+-calpain EF2 (146-153, 163-173) | (9.772, -1.548, -4.566) | 61.101 | 83.150 | 127 |
| Ca2+-calpain EF3 (176-183, 193-203) | (9.870, -0.864, -4.412) | 37.933 | 107.594 | 105 |
| Ca2+-calpain EF4 (211-218, 228-238) | (3.406, -9.892, -5.999) | 45.584 | 17.174 | 199 |
| Ca2+-calpain EF5 (241-248, 260-270) | (12.743, 6.493, -0.271) | 18.720 | 156.366 | 127 |
NB: values obtained using apo-CaM EF1 (as in refcam.pdb) as the reference EF-hand.