Figure 5: Movements of the N-terminal domain of the aspartate/glutamate carrier in response to calcium binding.

(a) The calcium-bound state of the N-terminal domain of citrin with the C-terminal helix bound. The C-terminal helix is shown in a cartoon representation and is coloured wheat. The bound calcium ions are shown as green spheres. The red semi-circles indicate the opening of a vestibule. (b) The calcium-free state of the N-terminal domain of aralar (chain B) with the linker loop in red. The red lines indicate the closure of the vestibule. The cartoon representations are coloured as in Fig. 1a. The conformational change between states involves a rotation of EF-hands 1–2 relative to the static domain of EF-hands 4–8. The rotations are shown by circles with black sectors and arrows marking the angle and direction of rotation, and a black line marking the rotation axis. Magenta spheres highlight the bending region corresponding to residues 82 (aralar) and 83 (citrin). The C-terminal helix and the linker loop are indicated with wheat and red coloured arrow heads, respectively. (c) A view down the rotation axis, showing the conformational change between calcium-bound citrin and calcium-free aralar. Citrin is shown as a cartoon, coloured as in Fig. 1a, with the C-terminal domain removed for clarity. The calcium-free state of aralar is shown as a grey cartoon.