Rapid Identification of Protein Biomarkers of Escherichia coli O157:H7 by Matrix-Assisted Laser Desorption Ionization-Time-of-Flight−Time-of-Flight Mass Spectrometry and Top-Down Proteomi
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- 作者：Clifton K. Fagerquist ; Brandon R. Garbus ; William G. Miller ; Katherine E. Williams ; Emma Yee ; Anna H. Bates ; Sobhn Boyle ; Leslie A. Harden ; Michael B. Cooley ; Robert E. Mandrell
- 刊名：Analytical Chemistry
- 出版年：2010
- 出版时间：April 1, 2010
- 年：2010
- 卷：82
- 期：7
- 页码：2717-2725
- 全文大小：289K
- 年卷期：v.82,no.7(April 1, 2010)
- ISSN：1520-6882
文摘
Six protein biomarkers from two strains of Escherichia coli O157:H7 and one non-O157:H7, nonpathogenic strain of E. coli have been identified by matrix-assisted laser desorption ionization time-of-flight−time-of-flight tandem mass spectrometry (MALDI-TOF−TOF-MS/MS) and top-down proteomics. Proteins were extracted from bacterial cell lysates, ionized by MALDI, and analyzed by MS/MS. Protein biomarker ions were identified from their sequence-specific fragment ions by comparison to a database of in silico fragment ions derived from bacterial protein sequences. Web-based software, developed in-house, was used to rapidly compare the mass-to-charge (m/z) of MS/MS fragment ions to the m/z of in silico fragment ions derived from hundreds of bacterial protein sequences. A peak matching algorithm and a p-value algorithm were used to independently score and rank identifications on the basis of the number of MS/MS-in silico matches. The six proteins identified were the acid stress chaperone-like proteins, HdeA and HdeB; the cold shock protein, CspC; the YbgS (or homeobox protein); the putative stress-response protein YjbJ (or CsbD family protein); and a protein of unknown function, YahO. HdeA, HdeB, YbgS, and YahO proteins were found to be modified post-translationally with removal of an N-terminal signal peptide. Gene sequencing of hdeA, hdeB, cspC, ybgS, yahO, and yjbJ for 11 strains of E. coli O157:H7 and 7 strains of the “near-neighbor” serotype O55:H7 revealed a high degree sequence homology between these two serotypes. Although it was not possible to distinguish O157:H7 from O55:H7 from these six biomarkers, it was possible to distinguish E. coli O157:H7 from a nonpathogenic E. coli by top-down proteomics of the YahO and YbgS. In the case of the YahO protein, a single amino acid residue substitution in its sequence (resulting in a molecular weight difference of only 1 Da) was sufficient to distinguish E. coli O157:H7 from a non-O157:H7, nonpathogenic E. coli by MALDI-TOF−TOF-MS/MS, whereas this would be difficult to distinguish by MALDI-TOF-MS. Finally, a protein biomarker ion at m/z 9060 observed in the MS spectra of non-O157:H7 E. coli strains but absent from MS spectra of E. coli O157:H7 strains was identified by top-down analysis to be the HdeB acid stress chaperone-like protein consistent with previous identifications by gene sequencing and bottom-up proteomics.