Backbone structural comparison for the two VP55 monomer molecules in the asymmetric unit. (a) Structural overlay: molecule A, cyan; molecule B, magenta. The N-terminal domain lies on the right-hand side and the C-terminal domain lies on the left. The 118–129 loop is at the bottom. (b) R.m.s. deviations for the two molecules. Domain boundaries are indicated by blue vertical lines (the region between the N-terminal and central domains encompasses the crossover helix and two adjoining loops).