Lipid A, a constituent of lipopolysaccharides, is essential for the growth and virulence of most Gram-negative bacteria. This makes its biosynthetic enzymes potential targets for development of new antibacterial agents. The first step of lipid A biosynthesis is catalyzed by the enzyme UDP-N-acetylglucosamine acyltransferase (LpxA). LpxA from the pathogenic bacterium Helicobacter pylori has been overexpressed in Escherichia coli and crystallized at 297 K using ammonium sulfate and sodium/potassium tartrate as precipitants in the presence of a detergent. Diffraction data to 2.1 A resolution have been collected from a native crystal. The crystal belongs to space group P6(3)22, with unit-cell parameters a = b = 90.69, c = 148.20 A. The asymmetric unit contains one subunit of LpxA, with a crystal volume per protein mass (V(M)) of 2.87 A(3) Da(-1) and a solvent content of 57.1%.