Location: Produce Safety and Microbiology ResearchTitle: The effect of asparagine and the aspartic acid fragmentation mechanism on post-source decay of intact Shiga toxin (Stx) from Shiga toxin-producing Escherichia coli (STEC) using MALDI-TOF-TOF mass spectrometry
|Fagerquist, Clifton - Keith|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/18/2019
Publication Date: 4/3/2019
Citation: Fagerquist, C.K., Zaragoza, W.J. 2019. The effect of asparagine and the aspartic acid fragmentation mechanism on post-source decay of intact Shiga toxin (Stx) from Shiga toxin-producing Escherichia coli (STEC) using MALDI-TOF-TOF mass spectrometry [abstract]. Mass Spectrometry: Application to the Clinical Lab 2019, March 31-April 4, 2019, Palm Springs, CA.
Technical Abstract: We have examined by tandem mass spectrometry (MS/MS) post-source decay (PSD) the unimolecular dissociation of a number Shiga toxin (Stx) B-subunits expressed by Shiga toxin-producing Escherichia coli (STEC) using matrix-assisted laser desorption/ionization time-of-flight-time-of-flight (MALDI-TOF-TOF) mass spectrometry. In addition to polypeptide backbone cleavage on the C-terminal side of aspartic acid (D) and glutamic acid (E) residues consistent with the aspartic acid fragmentation mechanism, we also observe cleavage on the C-terminal side of asparagine (N) residues. To the best of our knowledge, there have been no previous reports of asparagine undergoing an aspartic acid effect-like rearrangement leading to peptide or polypeptide backbone cleavage. We have examined this phenomenon in a number of nearly identical B-subunit sequences of Stx2. This unexpected N-based fragmentation channel presents unique challenges for top-down proteomic identification if the goal is to distinguish slight differences in sequence, e.g. D ' N substitution that results in a protein mass difference of 1 Da and a 1 Th difference in m/z of fragment ions containing this substitution.