Crystallization and preliminary crystallographic analysis of an Ig-domain-encompassing fragment of the giant adhesion protein SiiE fromSalmonella enterica

Salmonella infections can be life-threatening. SiiE is a giant adhesion molecule of 5559 amino acids that is encoded in Salmonella pathogenicity island 4 (SPI4) and that promotes the initial contact between the pathogen and polarized epithelial cells in the intestine of the host. Starting from an engineered deletion version of SiiE (mini-SiiE; 97 kDa), limited proteolysis was used to reproducibly generate a 30 kDa fragment that readily crystallized. Mass spectrometry hints that this fragment spans the predicted Ig domains 50–52 of SiiE. Crystals of both native and selenomethionine-labelled protein could be obtained in space group C2 and diffraction data were recorded to a resolution of 1.85 Å.