Expression, crystallization and preliminary X-ray crystallographic analysis ofD-alanine-D-alanine ligase from OXA-23-producingAcinetobacter baumanniiK0420859
Acinetobacter baumanniicauses bacteraemia, pneumonia, other respiratory-tract and urinary-tract infections in humans. OXA-23 carbapenemase-producingA. baumanniiK0420859 (A. baumanniiOXA-23) is resistant to carbapenem, a common antibacterial drug. To develop an efficient and novel antibacterial drug againstA. baumanniiOXA-23, D-alanine-D-alanine ligase, which is essential in bacterial cell-wall synthesis, is of interest. Here, the D-alanine-D-alanine ligase (AbDdl) gene fromA. baumanniiOXA-23 was cloned and expressed, and theAbDdl protein was purified and crystallized; this enzyme can be used as a novel target for an antibacterial drug againstA. baumanniiOXA-23. TheAbDdl crystal diffracted to a resolution of 2.8 Å and belonged to the orthorhombic space groupP212121, with unit-cell parametersa= 113.4,b= 116.7,c= 176.5 Å, a correspondingVMof 2.8 Å3 Da−1and a solvent content of 56.3%, and six protomers in the asymmetric unit.