Purification, crystallization and preliminary X‐ray diffraction analysis of GatD, a glutamine amidotransferase‐like protein from Staphylococcus aureus peptidoglycan

Amidation of peptidoglycan is an essential feature in Staphylococcus aureus that is necessary for resistance to β‐lactams and lysozyme. GatD, a 27 kDa type I glutamine amidotransferase‐like protein, together with MurT ligase, catalyses the amidation reaction of the glutamic acid residues of the peptidoglycan of S. aureus . The native and the selenomethionine‐derivative proteins were crystallized using the sitting‐drop vapour‐diffusion method with polyethylene glycol, sodium acetate and calcium acetate. The crystals obtained diffracted beyond 1.85 and 2.25 Å, respectively, and belonged to space group P 2 1 2 1 2 1 . X‐ray diffraction data sets were collected at Diamond Light Source (on beamlines I02 and I04) and were used to obtain initial phases.