Structural analysis of interlaced MBP dimers. (A) 90° views of maltose-free MBPeng-KFLFAK. Chains are coloured in magenta and cyan. The region of arm-exchange is boxed. A monomeric MBP in its maltose-bound closed state is superimposed (grey, PDB accession 3woa). The double-headed arrow indicates the domain-movement associated with open and closed MBP forms. (B) Maltose-bound MBPeng-KFLPYK2 is shown in grey (chain A) and orange (chain B). (C) Omit maps (green mesh) showing the arm-exchange region (residues 172–177) for MBPeng-KFLFAK (top) and MBPeng-KFLPYK2 (bottom). Figures were prepared using PyMol 184.108.40.206 (https://pymol.org).