Interactions along the spectrin tetramerization domain interface are extensive. (A) The interacting surfaces of the tetramerization domain span nearly the entire composite spectrin repeat (α-spectrin shown in blue, β-spectrin shown in yellow). The interface of the complex is opened to the reader such that the interacting surface on each molecule is viewable. Specific side chains that make contact in the crystal structure are shown as sticks and labeled. (B) The molecular surfaces of α0-1 (blue, surface that interacts with β16-17 in green) and β16-17 (yellow, surface that interacts with α0-1 in red) indicate the extent of binding along these 2 molecules. (C) The electrostatic surfaces of α0 and β17 show some charge complementarity, the electrostatic map was contoured at 15 ± k_BT/e. Views in panels B and C are similar to those in panel A, with both of the interacting surfaces turned to face the reader.