N-Chlorotaurine Inacitvates Shiga Toxin Figure 6. Oxidation of thio groups and aromatic groups of Stx2 detected with mass spectrometry. Bands a-f from the gels, as depicted for one representative in Figure 5, were analyzed with mass spectrometry after in-gel digestion. Similar results gained from three independent experiments are shown. Positions and occurrence in bands are demonstrated. Amino acids 1–22 (subunit A) and 1–19 (subunit B), respectively, comprise the signal peptides. (A) Oxidation of all methionines and cysteines of subunit A occurred. Positions of oxidized amino acids in the sequence are shown and their mono- to tri-oxidation in relation to the bands excised from the gels. (B) Chlorination of phenylalanine, tyrosine, and histidine of subunit A. (C) Oxidation of methionine and chlorination of tyrosine of subunit B. doi:10.1371/journal.pone.0047105.g006 PLOS ONE | www.plosone.org 10 November 2012 | Volume 7 | Issue 11 | e47105