Top-down proteomic identification of furin-cleaved ?-subunit of Shiga toxin 2 from Escherichia coli O157:H7 using MALDI-TOF-TOF-MS/MS.

ABSTRACT: A method has been developed to identify the ?-subunit of Shiga toxin 2 (?-Stx2) from Escherichia coli O157:H7 using matrix-assisted laser desorption/ionization time-of-flight-time-of-flight tandem mass spectrometry (MALDI-TOF-TOF-MS/MS) and top-down proteomics using web-based software developed in-house. Expression of Stx2 was induced by culturing E. coli O157:H7 on solid agar supplemented with an antibiotic that elicits the bacterial SOS-response. Bacterial cell lysates were incubated in the presence of furin, a human enzyme, that cleaves ?-Stx2 into A1 (~28?kDa) and A2 (~5?kDa) protein fragments. A subsequent disulfide reduction step unlinked A1 from A2. MALDI-TOF-MS of the furin-digested/disulfide-reduced sample showed a peak at mass-to-charge (m/z) 5286 that corresponded to the A2 fragment. No peak was observed that corresponded to the A1 fragment although its presence was confirmed by bottom-up proteomics. The peak at m/z 5286 was definitively identified by MALDI-TOF-TOF-MS/MS and top-down proteomics as the A2 fragment of ?-Stx2.

SUBMITTER: Fagerquist CK 

PROVIDER: S-EPMC3038467 | biostudies-literature | 2010

REPOSITORIES: biostudies-literature