Structure-based sequence alignment of NDM-1, IMP-1, VIM-2 and ccrA. Alignments were generated using LGA with NDM-1 (3q6x_A) as the reference. Capitalized amino acids indicate structural residue-residue correspondence, whereas lowercase amino acids indicate regions in MBLs where no structural alignment with NDM-1 can be identified. Regions of interested are denoted by boxes and labeled as the mobile flap (1, blue) (residues 65-73 in NDM-1; 23-31 in IMP-1; 59-67 in VIM-2; and 44-52 in ccrA), the linker region including anchoring regions (2, blue) (residues 141-193 in NDM-1; 98-143 in IMP-1; 138-200 in VIM-2; and 120-166 in ccrA), the non-aligning linker region core (3, red) (residues 163-179 in NDM-1; 120-129 in IMP-1; 174-186 in VIM-2; and 142-152 in ccrA), and the L10 loop (4, blue) (residues 210-227 in NDM-1; 160-174 in IMP-1; 223-240 in VIM-2; and 183-200 in ccrA). Notably, ccrA is the only B1 MBL gap free with respect to NDM-1 outside of the linker region.