Crystallisation and Preliminary Crystallographic Analysis of Helicobacter pylori Periplasmic Binding Protein YckK

Helicobacter pylori infection can lead to the development of gastric and duodenal ulcers and gastric cancer. In recent years, the efficacy of the standard therapy has been falling, necessitating ongoing efforts to identify new drug targets. Due to their important role in chemotaxis and nutrient uptake, periplasmic binding proteins (PBPs) represent potential targets for new antimicrobial agents that have not yet been fully explored and exploited. The H. pylori PBP YckK is homologous to polar amino acid-binding proteins from other bacteria. The yckK gene overlaps the gene tcyBa gene annotated as a polar amino acid-transporting permease. Purified recombinant YckK behaved as a monomer in solution. Crystals of YckK were grown by the hanging drop vapour diffusion method using PEG 3350 as the precipitating agent. The crystals belong to the primitive triclinic space group P1 with unit cell parameters a = 63.0, b = 63.5, c = 74.6 angstrom, alpha = 72.5, beta = 68.3, gamma = 69.4 degrees. X-ray diffraction data were collected to 1.8 angstrom resolution using synchrotron radiation. Molecular replacement using this data revealed that the asymmetric unit contains three subunits: two in the open and one in the closed conformation.