Overall structures of PurLs. The A1, B1, A2 and B2 domains are indicated in green, blue, magenta and cyan, respectively. The N-terminal flanking sequence and the linker between the B1 and A2 domains are indicated in grey and yellow, respectively. (a) TtPurL, (b) TmPurL (PDB entry 2hru
), (c) StPurL (PDB entry 1t3t
). The locations of bound ADP, PO43− and Mg2+ are also shown in (a).