Cloning, expression, purification and crystallization of an endotoxin‐biosynthesis enzyme from Neisseria meningitidis

The enzyme phosphoethanolamine transferase A is involved in the addition of phosphoethanolamine moieties to lipid A in Neisseria meningitidis . The enzyme is composed of an N‐terminal transmembrane domain and a C‐terminal soluble domain that is present in the periplasm of the bacteria. A membrane‐deletion construct of the enzyme was designed and expressed in Escherichia coli . Well ordered crystals that diffracted to 1.7 Å resolution were obtained by carrying out a limited trypsin digestion of the protein to remove a predicted N‐terminal disordered portion. The crystals belonged to space group P 2 1 , with unit‐cell parameters a = 44.3, b = 71.6, c = 49.9 Å, β = 109.2°, and contained one molecule in the asymmetric unit.