Expression, purification and preliminary crystallographic analysis of dipeptidyl peptidase IV from Porphyromonas gingivalis

The asaccharolytic periodontopathogen Porphyromonas gingivalis produces membrane-anchored proteases such as dipeptidyl peptidase IV that are involved in the destruction of host periodontal tissue. The extracellular domain of this enzyme was overexpressed in Escherichia coli as an N-terminal His-tag fusion protein, purified using standard metal-affinity chromatography and crystallized using the hanging-drop vapour-diffusion technique in 40% 2-methyl-2,4-pentanediol and 100 mM Tris-HCl pH 8.0. Diffraction data to 2.7 Angstrom resolution were collected using synchrotron radiation. The crystals belong to space group P2(1), with unit-cell parameters a = 117.0, b = 112.9, c = 310.0 Angstrom, beta = 95.0degrees. There are ten molecules per asymmetric unit, indicating a solvent content of 50%. Data were also collected from selenomethionine-derived crystals and structure solution by SAD or MAD is in progress.