Fig. 1

Cartoon representation of DEL-II (chains -A and -B; pink and light pink) as viewed down the catalytic cleft and superposed with DEL-I (PDB entry 5v8g, green) and DEL-III (two crystal forms: PDB entry 5v92 (orthorhombic form) coloured orange and light orange (chains -A and -B); and PDB entry 5v94 (cubic form) coloured blue and light blue (chains -A and -B)). Positions 37 and 71 are shown as sticks. The structures differ most in loop regions; loop101–103, and loop 67–73. DEL-II chain B differs most starkly from the ensemble at loop 67–73 (light pink loop and text), including Arg71, the side chain of which is disordered