Expression, limited proteolysis and preliminary crystallographic analysis of IpaD, a component of the Shigella flexneri type III secretion system

Academic Article


  • IpaD, the putative needle-tip protein of the Shigella flexneri type III secretion system, has been overexpressed and purified. Crystals were grown of the native protein in space group P212121, with unit-cell parameters a = 55.9, b = 100.7, c = 112.0 Å, and data were collected to 2.9 Å resolution. Analysis of the native Patterson map revealed a peak at 50% of the origin on the Harker section v = 0.5, suggesting twofold non-crystallographic symmetry parallel to the b crystallographic axis. As attempts to derivatize or grow selenomethionine-labelled protein crystals failed, in-drop proteolysis was used to produce new crystal forms. A trace amount of subtilisin Carlsberg was added to IpaD before sparse-matrix screening, resulting in the production of several new crystal forms. This approach produced SeMet-labelled crystals and diffraction data were collected to 3.2 Å resolution. The SeMet crystals belong to space group C2, with unit-cell parameters a = 139.4, b = 45.0, c = 99.5 Å, β = 107.9°. An anomalous difference Patterson map revealed peaks on the Harker section v = 0, while the self-rotation function indicates the presence of a twofold noncrystallographic symmetry axis, which is consistent with two molecules per asymmetric unit. © 2006 International Union of Crystallography All rights reserved.
  • Authors

    Digital Object Identifier (doi)

    Pubmed Id

  • 2319317
  • Author List

  • Johnson S; Roversi P; Espina M; Deane JE; Birket S; Picking WD; Blocker A; Picking WL; Lea SM
  • Start Page

  • 865
  • End Page

  • 868
  • Volume

  • 62
  • Issue

  • 9