Figure 1.

Overall structure of Deg5 (S266A) and binding of Ca²⁺ ions. (a) Side and top views of the Deg5 (S266A) trimer with each protomer coloured differently. (b) Ca²⁺ ions binding to Deg5 (S266A). Top and left, electrostatic potential distributions of the inner surface of the trimer. Electrostatic potential was calculated using PyMOL. Blue and red represent positive and negative charge potentials on a scale between +75 and −75kT e⁻¹, respectively. Top and right, Ca²⁺ ions binding to the convex side of the trimer. Bottom, Ca²⁺ ions binding to the central channel of the Deg5 trimer. Ca²⁺ ions and waters are shown as spheres and are coloured yellow and purple, respectively. Residues interacting with Ca²⁺ ions are shown as sticks and are labelled. Salt bridges formed between Deg5 and Ca²⁺ ions are presented as black dashed lines. (c) Analytical SEC of Deg5 (S266A) (blue), Deg5 (S266A) dialyzed against EDTA (red) and Deg5 (S266A/E87A/D260A) triple mutant (green). The trimeric peak is indicated by an arrow.