Crystallization and sulfur SAD phasing of AggA, the major subunit of aggregative adherence fimbriae type I from the Escherichia coli strain that caused an outbreak of haemolytic-uraemic syndrome in Germany

The outbreak of Shiga toxin-producing Escherichia coli O104:H4 infection in Germany in 2011 was associated with significant mortality and morbidity owing to the progressive development of haemolytic-uraemic syndrome. The outbreak strain emerged recently as a result of horizontal transfer events leading to the acquisition of a number of virulence factors. Among them, aggregative adherence fimbriae type I (AAF/I) are considered to be particularly important since they are involved in the initial attachment of bacteria to the intestinal mucosa. Here, the crystallization and preliminary X-ray diffraction analysis of the major subunit of AAF/I, AggA, are reported. Crystallization of recombinant donor-strand complemented AggA was performed by the vapour-diffusion method. The crystals diffracted to 1.55 Å resolution and belonged to the orthorhombic space group C222₁, with unit-cell parameters a = 77.83, b = 80.17, c = 91.42 Å. Despite a low sulfur content of the protein [0.57%(w/w)], sufficiently accurate initial phases were derived from a sulfur SAD experiment.