Purification, crystallization and preliminary crystallographic analysis of the adhesion domain of Epf from Streptococcus pyogenes

The extracellular protein Epf from Streptococcus pyogenes is important for streptococcal adhesion to human epithelial cells. However, Epf has no sequence identity to any protein of known structure or function. Thus, several predicted domains of the 205 kDa protein Epf were cloned separately and expressed in Escherichia coli. The N-terminal domain of Epf was crystallized in space groups P2₁ and P2₁2₁2₁ in the presence of the protease chymotrypsin. Mass spectrometry showed that the species crystallized corresponded to a fragment comprising residues 52-357 of Epf. Complete data sets were collected to 2.0 and 1.6 Å resolution, respectively, at the Australian Synchrotron.