Figure 3: Interactions between structural elements.

(a) Interactions between N- and C-terminal domains of citrin. Chain A is coloured according to the scheme in Fig. 1a. Hydrogen bonds between the domains are shown as black dotted lines, with donor and acceptor residues shown in stick representation. The salt-bridge interaction between residues Lys23 and Asp635 is shown as a green dotted line. Residues involved in hydrophobic contacts are shown as sticks. The water molecules involved in hydrogen-bonding networks are shown as blue spheres. (b) Interactions stabilizing the linker loop, which links the C-terminus of the N-terminal domain to the carrier domain, as seen in the calcium-free state of aralar. Chain B is depicted. Hydrogen bonds are shown as black dotted lines, with donor and acceptor residues shown as sticks. The orientation of the structures in the two panels is similar.