Fig. 2. A-view along the interface perpendicular to the pseudo symmetry axis. From top to bottom the three layers are seen: antiparallel sheet; mixed sheet with a P-loop; and helix 1 and helical layer. Colouring is as in Figure 1 except that the conserved regions Walker-A, Walker-B, signature motif, D-loop, switch from monomer A and the ‘lid’ region from monomer B are marked by red colouring with yellow outlines. Labels indicate the numbers of strands and helices according to the numbering given in Figure 3.