Expression, crystallization and preliminary X-ray crystallographic analysis of alanine racemase from Acinetobacter baumannii OXA-23

Acinetobacter baumannii has received much attention owing to its exceptional ability to develop resistance to currently available antibiotics. Alanine racemase (ALR) catalyzes the racemization of l-alanine to D-alanine with pyridoxal 5'-phosphate (PLP) as a cofactor. The d-alanine product is an essential component of the bacterial cell wall and ALR is a potential target for the development of novel antibacterial drugs. The alr gene from A. baumannii was cloned and the protein (AbALR) was expressed, purified and crystallized. The AbALR crystal diffracted to 2.3 angstrom resolution and belonged to the primitive orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 55.1, b = 85.0, c = 167.7 angstrom. Two protomers were present in the asymmetric unit, with a corresponding V-M value of 2.3 angstrom(3) Da(-1) and a solvent content of 47.5%.