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 3

MS/MS of the precursor ion at m/z 5286 in Figure 2. Fragment ions marked with a solid circle were also observed in the MS/MS spectrum of the precursor ion at m/z 5250 (Figure S1). Fragment ions matched to in silico fragments ions of α _A2-Stx2 are identified by their ion type/number and the two amino acid residues adjacent to the site of polypeptide cleavage. Sequence of α _A2-Stx2. Asterisk indicates site of gas phase fragmentation with corresponding ion type/number. D, E, and P residues are highlighted in red.