Top-Down Proteomic Identification of Furin-Cleaved α-Subunit of Shiga Toxin 2 from Escherichia coli O157:H7 Using MALDI-TOF-TOF-MS/MS

Figure 1

Sequence of α-Stx2 from E. coli O157:H7 (EDL933). A 22-residue signal peptide (in bold) is removed in the mature protein, and cysteines involved in an intramolecular disulfide bond (𝑆⋯𝑆) are boxed. Potential furin cleavage recognition sites (RXXR) are boxed. An asterisk (*) marks the observed furin cleavage site. In eukaryotic cells, after disulfide reduction, the catalytically active α _A1-Stx2 fragment is translocated to the cytosol and the α _A2-Stx2 fragment remains associated with the β-pentamer.