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Fagerquist CK, Shi Y, Dodd CE. Toxin and phage production from pathogenic E. coli by antibiotic induction analyzed by chemical reduction, MALDI-TOF-TOF mass spectrometry and top-down proteomic analysis. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2023; 37:e9505. [PMID: 36905351 DOI: 10.1002/rcm.9505] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 02/18/2023] [Accepted: 03/08/2023] [Indexed: 06/18/2023]
Abstract
RATIONALE Shiga toxin-producing Escherichia coli (STEC) are an ongoing threat to public health and agriculture. Our laboratory has developed a rapid method for identification of Shiga toxin (Stx), bacteriophage, and host proteins produced from STEC. We demonstrate this technique on two genomically sequenced STEC O145:H28 strains linked to two major outbreaks of foodborne illness occurring in 2007 (Belgium) and 2010 (Arizona). METHODS Our approach was to induce expression of stx, prophage, and host genes by antibiotic exposure, chemically reduce samples, and identify protein biomarkers from unfractionated samples using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, tandem mass spectrometry (MS/MS), and post-source decay (PSD). The protein mass and prominent fragment ions were used to identify protein sequences using top-down proteomic software developed in-house. Prominent fragment ions are the result of polypeptide backbone cleavage resulting from the aspartic acid effect fragmentation mechanism. RESULTS The B-subunit of Stx and acid-stress proteins HdeA and HdeB were identified in both STEC strains in their intramolecular disulfide bond-intact and reduced states. In addition, two cysteine-containing phage tail proteins were detected and identified from the Arizona strain but only under reducing conditions, which suggests that bacteriophage complexes are bound by intermolecular disulfide bonds. An acyl carrier protein (ACP) and a phosphocarrier protein were also identified from the Belgium strain. ACP was post-translationally modified with attachment of a phosphopantetheine linker at residue S36. The abundance of ACP (plus linker) was significantly increased on chemical reduction, suggesting the release of fatty acids bound to the ACP + linker at a thioester bond. MS/MS-PSD revealed dissociative loss of the linker from the precursor ion as well as fragment ions with and without the attached linker consistent with its attachment at S36. CONCLUSIONS This study demonstrates the advantages of chemical reduction in facilitating the detection and top-down identification of protein biomarkers of pathogenic bacteria.
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Affiliation(s)
- Clifton K Fagerquist
- US Department of Agriculture, Produce Safety & Microbiology, Western Regional Research Center, Agricultural Research Service, Albany, CA, USA
| | - Yanlin Shi
- US Department of Agriculture, Produce Safety & Microbiology, Western Regional Research Center, Agricultural Research Service, Albany, CA, USA
| | - Claire E Dodd
- US Department of Agriculture, Produce Safety & Microbiology, Western Regional Research Center, Agricultural Research Service, Albany, CA, USA
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Liu R, Xia S, Li H. Native top-down mass spectrometry for higher-order structural characterization of proteins and complexes. MASS SPECTROMETRY REVIEWS 2022:e21793. [PMID: 35757976 DOI: 10.1002/mas.21793] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 05/23/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
Progress in structural biology research has led to a high demand for powerful and yet complementary analytical tools for structural characterization of proteins and protein complexes. This demand has significantly increased interest in native mass spectrometry (nMS), particularly native top-down mass spectrometry (nTDMS) in the past decade. This review highlights recent advances in nTDMS for structural research of biological assemblies, with a particular focus on the extra multi-layers of information enabled by TDMS. We include a short introduction of sample preparation and ionization to nMS, tandem fragmentation techniques as well as mass analyzers and software/analysis pipelines used for nTDMS. We highlight unique structural information offered by nTDMS and examples of its broad range of applications in proteins, protein-ligand interactions (metal, cofactor/drug, DNA/RNA, and protein), therapeutic antibodies and antigen-antibody complexes, membrane proteins, macromolecular machineries (ribosome, nucleosome, proteosome, and viruses), to endogenous protein complexes. The challenges, potential, along with perspectives of nTDMS methods for the analysis of proteins and protein assemblies in recombinant and biological samples are discussed.
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Affiliation(s)
- Ruijie Liu
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Shujun Xia
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Huilin Li
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
- Guangdong Key Laboratory of Chiral Molecule and Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
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Kubo Y, Ueda O, Nagamitsu S, Yamanishi H, Nakamura A, Komatsu M. Novel strategy of rapid typing of Shiga toxin-producing Escherichia coli using MALDI Biotyper and ClinProTools analysis. J Infect Chemother 2021; 27:1137-1142. [PMID: 33745812 DOI: 10.1016/j.jiac.2021.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 02/14/2021] [Accepted: 03/01/2021] [Indexed: 11/17/2022]
Abstract
INTRODUCTION Rapid detection of Shiga toxin-producing Escherichia coli (STEC) is essential. Matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows rapid, accurate, and low-cost microbial identification. We aimed to examine the discrimination ability of MALDI Biotyper (Bruker Daltonics) between STEC and non-STEC. METHODS In total, 234 strains (79 STEC strains and 155 non-STEC strains) isolated from stool between 2009 and 2014 were measured by MALDI Biotyper and mass spectra of 2000-20,000 m/z were analyzed with ClinProTools (Bruker Daltonics). Eighty-three strains were randomly extracted to produce STEC detection models using 3 algorithms, and 151 strains were used as validation samples to verify STEC detection performance and discrimination performance of Shiga toxins with the STEC detection models. RESULTS The STEC detection model with Quick Classifier (QC) algorithm was the most sensitive: sensitivity, 84.1% (37/44); specificity, 94.4% (101/107). Discrimination between STEC and non-STEC was excellent, but individual discrimination of Shiga toxins was not possible. CONCLUSION MALDI Biotyper may be a useful rapid diagnostic method for STEC infection.
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Affiliation(s)
- Yumi Kubo
- FALCO Biosystems K. K., Tokai Central Laboratory, Test Group Microbiology, Aichi, Japan.
| | | | - Sawa Nagamitsu
- FALCO Biosystems K. K., Okayama Laboratory, Test Group Microbiology, Okayama, Japan.
| | - Hachiro Yamanishi
- Department of Clinical Laboratory Science, Faculty of Health Care, Tenri Health Care University, Japan.
| | - Akihiro Nakamura
- Department of Clinical Laboratory Science, Faculty of Health Care, Tenri Health Care University, Japan.
| | - Masaru Komatsu
- Department of Clinical Laboratory Science, Faculty of Health Care, Tenri Health Care University, Japan.
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Fagerquist CK, Zaragoza WJ, Carter MQ. Top-Down Proteomic Identification of Shiga Toxin 1 and 2 from Pathogenic Escherichia coli Using MALDI-TOF-TOF Tandem Mass Spectrometry. Microorganisms 2019; 7:E488. [PMID: 31731469 PMCID: PMC6920754 DOI: 10.3390/microorganisms7110488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Revised: 10/17/2019] [Accepted: 10/23/2019] [Indexed: 12/14/2022] Open
Abstract
Shiga-toxin-producing Escherichia coli (STEC) are a burden on agriculture and a threat to public health. Rapid methods are needed to identify STEC strains and characterize the Shiga toxin (Stx) they produce. We analyzed three STEC strains for Stx expression, using antibiotic induction, matrix-assisted laser desorption/ionization time-of-flight-time-of-flight (MALDI-TOF-TOF) mass spectrometry, and top-down proteomic analysis. E. coli O157:H- strain 493/89 is a clinical isolate linked to an outbreak of hemolytic uremic syndrome (HUS) in Germany in the late 1980s. E. coli O145:H28 strains RM12367-C1 and RM14496-C1 were isolated from an agricultural region in California. The stx operon of the two environmental strains were determined by whole genome sequencing (WGS). STEC strain 493/89 expressed Shiga toxin 2a (Stx2a) as identified by tandem mass spectrometry (MS/MS) of its B-subunit that allowed identification of the type and subtype of the toxin. RM12367-C1 also expressed Stx2a as identified by its B-subunit. RM14496-C1 expressed Shiga toxin 1a (Stx1a) as identified from its B-subunit. The B-subunits of Stx1 and Stx2 both have an intramolecular disulfide bond. MS/MS was obtained on both the disulfide-bond-intact and disulfide-bond-reduced B-subunit, with the latter being used for top-down proteomic identification. Top-down proteomic analysis was consistent with WGS.
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Affiliation(s)
- Clifton K. Fagerquist
- Produce Safety & Microbiology, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany, CA 94710, USA; (W.J.Z.); (M.Q.C.)
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Top-down and middle-down proteomic analysis of Shiga toxin using MALDI-TOF-TOF mass spectrometry. MethodsX 2019; 6:815-826. [PMID: 31049298 PMCID: PMC6484209 DOI: 10.1016/j.mex.2019.04.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 04/10/2019] [Indexed: 11/22/2022] Open
Abstract
The method describes a step-by-step process for analysis of putative Shiga toxin-producing Escherichia coli (STEC) for expression of Shiga toxin (Stx). The technique utilizes antibiotic induction, mass spectrometry and top-down/middle-down proteomic analysis. Stx expression is induced by overnight culturing of a STEC strain on Luria-Bertani agar (LBA) supplemented with DNA-damaging antibiotics. Culturing on agar media avoids sample contamination from salts, small molecules, peptides, etc. present in broth media that would interfere with protein ionization by matrix-assisted laser desorption/ionization (MALDI). No mechanical lysis of bacterial cells is required to release the toxin as the antibiotic triggers the lytic cycle of the bacteriophage resulting in toxin expression and bacterial cell lysis. Unfractionated samples are analyzed by MALDI-time-of-flight-time-of-flight (MALDI-TOF-TOF) mass spectrometry and tandem mass spectrometry (MS/MS) using post-source decay (PSD). New features of the method are the following. •Each putative STEC strain is systematically screened for toxin expression using two different antibiotics at two different concentrations: ciprofloxacin at 10 and 20 ng mL-1 and mitomycin-C at 800 and 1200 ng mL-1 to determine the optimal antibiotic and concentration for toxin expression for each strain.•The grid-to-source voltage of MALDI-TOF-TOF is optimized to maximize PSD efficiency.
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Clinically-relevant Shiga toxin 2 subtypes from environmental Shiga toxin-producing Escherichia coli identified by top-down/middle-down proteomics and DNA sequencing. CLINICAL MASS SPECTROMETRY 2018; 11:27-36. [PMID: 34841070 DOI: 10.1016/j.clinms.2018.12.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 11/30/2018] [Accepted: 12/02/2018] [Indexed: 12/12/2022]
Abstract
Thirty-five environmental isolates of Shiga toxin-producing Escherichia coli (STEC) were analyzed by MALDI-TOF-TOF mass spectrometry, top-down/middle-down proteomics and DNA sequencing. Clinically-relevant Shiga toxin 2 (Stx2) produced by these STEC strains were subtyped based on MS and MS/MS (tandem mass spectrometry) of the intact B-subunit (top-down) and A2 fragment (middle-down) of the A-subunit using antibiotic-induced protein expression. Antibiotic induction of Stx2 was found to be strain dependent. By proteomic analysis, seventeen strains were identified as Stx2a, six strains as Stx2c, four strains as either Stx2a or 2c and eight strains as either Stx2a, 2c or 2d. DNA sequencing indicated only stx 2a and stx 2c genes as being present in these strains. Weak induction of Stx2 for certain strains made it difficult to distinguish between clinical subtypes by proteomic analysis. Very weak toxin induction in eight strains was consistent with a ∼1300 bp transposon insertion in the stx 2c A-subunit gene identified by DNA sequencing. DNA sequencing also revealed the presence of two bacteriophage (BP) in three strains with a stx 2a gene in each BP genome. Middle-down proteomic analysis of the A2 fragment confirmed expression of two stx 2a genes present in one of these strains based on a slight difference in the amino acid sequence (D ↔ E substitution) in the two A2 fragments.
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Key Words
- BP, bacteriophage
- ELISA, enzyme-linked immunoassay
- GB, gas phase basicity
- Gb3, globotriaosylceramide
- MALDI-TOF-TOF, matrix-assisted laser desorption/ionization time-of-flight-time-of-flight
- MS, mass spectrometry
- MS/MS, tandem mass spectrometry
- PCR, polymerase chain reaction
- STEC, Shiga toxin-producing Escherichia coli
- Stx, Shiga toxin
- Stx1, Shiga toxin 1
- Stx2, Shiga toxin 2
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Exploration of variations in proteome and metabolome for predictive diagnostics and personalized treatment algorithms: Innovative approach and examples for potential clinical application. J Proteomics 2018; 188:30-40. [DOI: 10.1016/j.jprot.2017.08.020] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 08/06/2017] [Accepted: 08/25/2017] [Indexed: 12/20/2022]
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8
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Zhan L, Liu Y, Xie X, Xiong C, Nie Z. Heat-Induced Rearrangement of the Disulfide Bond of Lactoglobulin Characterized by Multiply Charged MALDI-TOF/TOF Mass Spectrometry. Anal Chem 2018; 90:10670-10675. [DOI: 10.1021/acs.analchem.8b02563] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Lingpeng Zhan
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu Liu
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaobo Xie
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Caiqiao Xiong
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Zongxiu Nie
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- National Center for Mass Spectrometry in Beijing, Beijing 100190, China
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9
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Silva CJ. Food Forensics: Using Mass Spectrometry To Detect Foodborne Protein Contaminants, as Exemplified by Shiga Toxin Variants and Prion Strains. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:8435-8450. [PMID: 29860833 DOI: 10.1021/acs.jafc.8b01517] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Food forensicists need a variety of tools to detect the many possible food contaminants. As a result of its analytical flexibility, mass spectrometry is one of those tools. Use of the multiple reaction monitoring (MRM) method expands its use to quantitation as well as detection of infectious proteins (prions) and protein toxins, such as Shiga toxins. The sample processing steps inactivate prions and Shiga toxins; the proteins are digested with proteases to yield peptides suitable for MRM-based analysis. Prions are detected by their distinct physicochemical properties and differential covalent modification. Shiga toxin analysis is based on detecting peptides derived from the five identical binding B subunits comprising the toxin. 15N-labeled internal standards are prepared from cloned proteins. These examples illustrate the power of MRM, in that the same instrument can be used to safely detect and quantitate protein toxins, prions, and small molecules that might contaminate our food.
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Affiliation(s)
- Christopher J Silva
- Produce Safety and Microbiology Research Unit, Western Regional Research Center, Agricultural Research Service , United States Department of Agriculture , Albany , California 94710 , United States
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10
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Steil D, Pohlentz G, Legros N, Mormann M, Mellmann A, Karch H, Müthing J. Combining Mass Spectrometry, Surface Acoustic Wave Interaction Analysis, and Cell Viability Assays for Characterization of Shiga Toxin Subtypes of Pathogenic Escherichia coli Bacteria. Anal Chem 2018; 90:8989-8997. [PMID: 29939014 DOI: 10.1021/acs.analchem.8b01189] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Shiga toxin (Stx)-producing Escherichia coli (STEC) and enterohemorrhagic E. coli (EHEC) as a human pathogenic subgroup of STEC are characterized by releasing Stx AB5-toxin as the major virulence factor. Worldwide disseminated EHEC strains cause sporadic infections and outbreaks in the human population and swine pathogenic STEC strains represent greatly feared pathogens in pig breeding and fattening plants. Among the various Stx subtypes, Stx1a and Stx2a are of eminent clinical importance in human infections being associated with life-threatening hemorrhagic colitis and hemolytic uremic syndrome, whereas Stx2e subtype is associated with porcine edema disease with a generalized fatal outcome for the animals. Binding toward the glycosphingolipid globotriaosylceramide (Gb3Cer) is a common feature of all Stx subtypes analyzed so far. Here, we report on the development of a matched strategy combining (i) miniaturized one-step affinity purification of native Stx subtypes from culture supernatant of bacterial wild-type strains using Gb3-functionalized magnetic beads, (ii) structural analysis and identification of Stx holotoxins by electrospray ionization ion mobility mass spectrometry (ESI MS), (iii) functional Stx-receptor real-time interaction analysis employing the surface acoustic wave (SAW) technology, and (iv) Vero cell culture assays for determining Stx-caused cytotoxic effects. Structural investigations revealed diagnostic tryptic peptide ions for purified Stx1a, Stx2a, and Stx2e, respectively, and functional analysis resulted in characteristic binding kinetics of each Stx subtype. Cytotoxicity studies revealed differing toxin-mediated cell damage ranked with Stx1a > Stx2a > Stx2e. Collectively, this matched procedure represents a promising clinical application for the characterization of life-endangering Stx subtypes at the protein level.
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Affiliation(s)
- Daniel Steil
- Institute for Hygiene , University of Münster , Robert-Koch-Strasse 41 , D-48149 Münster , Germany
| | - Gottfried Pohlentz
- Institute for Hygiene , University of Münster , Robert-Koch-Strasse 41 , D-48149 Münster , Germany
| | - Nadine Legros
- Institute for Hygiene , University of Münster , Robert-Koch-Strasse 41 , D-48149 Münster , Germany
| | - Michael Mormann
- Institute for Hygiene , University of Münster , Robert-Koch-Strasse 41 , D-48149 Münster , Germany
| | - Alexander Mellmann
- Institute for Hygiene , University of Münster , Robert-Koch-Strasse 41 , D-48149 Münster , Germany.,Interdisciplinary Center for Clinical Research (IZKF) Münster , Domagkstrasse 3 , D-48149 Münster , Germany
| | - Helge Karch
- Institute for Hygiene , University of Münster , Robert-Koch-Strasse 41 , D-48149 Münster , Germany.,Interdisciplinary Center for Clinical Research (IZKF) Münster , Domagkstrasse 3 , D-48149 Münster , Germany
| | - Johannes Müthing
- Institute for Hygiene , University of Münster , Robert-Koch-Strasse 41 , D-48149 Münster , Germany.,Interdisciplinary Center for Clinical Research (IZKF) Münster , Domagkstrasse 3 , D-48149 Münster , Germany
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Lu M, Zhan X. The crucial role of multiomic approach in cancer research and clinically relevant outcomes. EPMA J 2018; 9:77-102. [PMID: 29515689 PMCID: PMC5833337 DOI: 10.1007/s13167-018-0128-8] [Citation(s) in RCA: 134] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 01/29/2018] [Indexed: 02/06/2023]
Abstract
Cancer with heavily economic and social burden is the hot point in the field of medical research. Some remarkable achievements have been made; however, the exact mechanisms of tumor initiation and development remain unclear. Cancer is a complex, whole-body disease that involves multiple abnormalities in the levels of DNA, RNA, protein, metabolite and medical imaging. Biological omics including genomics, transcriptomics, proteomics, metabolomics and radiomics aims to systematically understand carcinogenesis in different biological levels, which is driving the shift of cancer research paradigm from single parameter model to multi-parameter systematical model. The rapid development of various omics technologies is driving one to conveniently get multi-omics data, which accelerates predictive, preventive and personalized medicine (PPPM) practice allowing prediction of response with substantially increased accuracy, stratification of particular patients and eventual personalization of medicine. This review article describes the methodology, advances, and clinically relevant outcomes of different "omics" technologies in cancer research, and especially emphasizes the importance and scientific merit of integrating multi-omics in cancer research and clinically relevant outcomes.
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Affiliation(s)
- Miaolong Lu
- Key Laboratory of Cancer Proteomics of Chinese Ministry of Health, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008 People’s Republic of China
- Hunan Engineering Laboratory for Structural Biology and Drug Design, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008 People’s Republic of China
- State Local Joint Engineering Laboratory for Anticancer Drugs, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008 People’s Republic of China
| | - Xianquan Zhan
- Key Laboratory of Cancer Proteomics of Chinese Ministry of Health, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008 People’s Republic of China
- Hunan Engineering Laboratory for Structural Biology and Drug Design, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008 People’s Republic of China
- State Local Joint Engineering Laboratory for Anticancer Drugs, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008 People’s Republic of China
- The State Key Laboratory of Medical Genetics, Central South University, 88 Xiangya Road, Changsha, Hunan 410008 People’s Republic of China
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Vávrová A, Matoulková D, Balážová T, Šedo O. MALDI-TOF MS Analysis of Anaerobic Bacteria Isolated from Biofilm-Covered Surfaces in Brewery Bottling Halls. JOURNAL OF THE AMERICAN SOCIETY OF BREWING CHEMISTS 2018. [DOI: 10.1094/asbcj-2014-0324-01] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Andrea Vávrová
- Section of Microbiology, Department of Experimental Biology, Faculty of Science, Masaryk University, Tvrdého 14, 602 00 Brno, Czech Republic
| | - Dagmar Matoulková
- Department of Microbiology, Research Institute of Brewing and Malting, Plc., Lípová 15, 120 44 Prague 2, Czech Republic
| | - Tereza Balážová
- Section of Microbiology, Department of Experimental Biology, Faculty of Science, Masaryk University, Tvrdého 14, 602 00 Brno, Czech Republic
- Research Group Proteomics, CEITEC, Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Ondrej Šedo
- Research Group Proteomics, CEITEC, Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
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Fagerquist CK. Unlocking the proteomic information encoded in MALDI-TOF-MS data used for microbial identification and characterization. Expert Rev Proteomics 2016; 14:97-107. [DOI: 10.1080/14789450.2017.1260451] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Clifton K. Fagerquist
- United States Department of Agriculture (USDA), Agricultural Research Service, Albany, CA, USA
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14
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Fagerquist CK, Zaragoza WJ. Bacteriophage cell lysis of Shiga toxin-producing Escherichia coli for top-down proteomic identification of Shiga toxins 1 & 2 using matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:671-680. [PMID: 26864518 DOI: 10.1002/rcm.7507] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Revised: 01/05/2016] [Accepted: 01/09/2016] [Indexed: 06/05/2023]
Abstract
RATIONAL Analysis of bacteria by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) often relies upon sample preparation methods that result in cell lysis, e.g. bead-beating. However, Shiga toxin-producing Escherichia coli (STEC) can undergo bacteriophage-induced cell lysis triggered by antibiotic exposure that may allow greater selectivity of the proteins extracted. METHODS We have developed a sample preparation method for selective extraction of bacteriophage-encoded proteins and specifically Shiga toxins 1 and 2 (Stx1 & 2) expressed from STEC strains induced by DNA-damaging antibiotics. STEC strains were cultured overnight on agar supplemented with ciprofloxacin, mitomycin-C or an iron chelator to induce the bacteriophage lytic cycle with concomitant expression and release of Stx1 and/or Stx2. Sample preparation relied exclusively on bacteriophage lysis for release Stx into the extraction solution. RESULTS Three clinical STEC strains were analyzed by matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF-TOF-MS/MS) and top-down proteomics analysis: E. coli O157:H7 strain EDL933, E. coli O91:H21 strain B2F1 and E. coli O26:H11 strain ECRC #05.2217. The B-subunit of Stx1a of EDL933 was detected and identified even though it was ~100-fold less abundant than the B-subunit of Stx2a that had been identified previously for this strain. Two bacteriophage-encoded proteins were also identified: L0117 and L0136. The B-subunits of Stx2d of strain B2F1 and Stx1a of strain ECRC #05.2217 were also detected and identified. CONCLUSIONS Bacteriophage lysis appeared to enhance the detection sensitivity of Stx for these STEC strains compared to previous work using mechanical lysis. Detection/identification of other bacteriophage-encoded proteins (beyond Stx) tends to support the hypothesis of Stx release by bacteriophage cell lysis.
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Affiliation(s)
- Clifton K Fagerquist
- Produce Safety & Microbiology Research Unit, Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany, CA, 94710, USA
| | - William J Zaragoza
- Produce Safety & Microbiology Research Unit, Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany, CA, 94710, USA
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Silva CJ, Erickson-Beltran ML, Skinner CB, Patfield SA, He X. Mass Spectrometry-Based Method of Detecting and Distinguishing Type 1 and Type 2 Shiga-Like Toxins in Human Serum. Toxins (Basel) 2015; 7:5236-53. [PMID: 26633510 PMCID: PMC4690125 DOI: 10.3390/toxins7124875] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 10/28/2015] [Accepted: 11/09/2015] [Indexed: 01/18/2023] Open
Abstract
Shiga-like toxins (verotoxins) are responsible for the virulence associated with a variety of foodborne bacterial pathogens. Direct detection of toxins requires a specific and sensitive technique. In this study, we describe a mass spectrometry-based method of analyzing the tryptic decapeptides derived from the non-toxic B subunits. A gene encoding a single protein that yields a set of relevant peptides upon digestion with trypsin was designed. The (15)N-labeled protein was prepared by growing the expressing bacteria in minimal medium supplemented with (15)NH₄Cl. Trypsin digestion of the (15)N-labeled protein yields a set of (15)N-labeled peptides for use as internal standards to identify and quantify Shiga or Shiga-like toxins. We determined that this approach can be used to detect, quantify and distinguish among the known Shiga toxins (Stx) and Shiga-like toxins (Stx1 and Stx2) in the low attomole range (per injection) in complex media, including human serum. Furthermore, Stx1a could be detected and distinguished from the newly identified Stx1e in complex media. As new Shiga-like toxins are identified, this approach can be readily modified to detect them. Since intact toxins are digested with trypsin prior to analysis, the handling of intact Shiga toxins is minimized. The analysis can be accomplished within 5 h.
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Affiliation(s)
- Christopher J Silva
- Western Regional Research Center, United States Department of Agriculture, Albany, CA 94710, USA.
| | | | - Craig B Skinner
- Western Regional Research Center, United States Department of Agriculture, Albany, CA 94710, USA.
| | - Stephanie A Patfield
- Western Regional Research Center, United States Department of Agriculture, Albany, CA 94710, USA.
| | - Xiaohua He
- Western Regional Research Center, United States Department of Agriculture, Albany, CA 94710, USA.
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Fagerquist CK, Zaragoza WJ. Shiga toxin 2 subtypes of enterohemorrhagic E. coli O157:H- E32511 analyzed by RT-qPCR and top-down proteomics using MALDI-TOF-TOF-MS. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:788-799. [PMID: 25667061 DOI: 10.1007/s13361-015-1076-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 01/07/2015] [Accepted: 01/07/2015] [Indexed: 06/04/2023]
Abstract
We have measured the relative abundance of the B-subunits and mRNA transcripts of two Stx2 subtypes present in Shiga toxin-producing Escherichia coli (STEC) O157:H- strain E32511 using matrix-assisted laser desorption/ionization time-of-flight-time-of-flight tandem mass spectrometry (MALDI-TOF-TOF-MS/MS) with post source decay (PSD) and real time-quantitative polymerase chain reaction (RT-qPCR). Stx2a and Stx2c in STEC strain E32511 were quantified from the integrated peak area of their singly charged disulfide-intact B-subunit ions at m/z ~7819 and m/z ~7774, respectively. We found that the Stx2a subtype was 21-fold more abundant than the Stx2c subtype. The two amino acid substitutions (16D ↔ 16 N and 24D ↔ 24A) that distinguish Stx2a from Stx2c not only result in a mass difference of 45 Da between their respective B-subunits but also result in distinctly different fragmentation channels by MS/MS-PSD because both substitutions involve an aspartic acid (D) residue. Importantly, these two substitutions have also been linked to differences in subtype toxicity. We measured the relative abundances of mRNA transcripts using RT-qPCR and determined that the stx2a transcript is 13-fold more abundant than stx2c transcript. In silico secondary structure analysis of the full mRNA operons of stx2a and stx2c suggest that transcript structural differences may also contribute to a relative increase of Stx2a over Stx2c. In consequence, toxin expression may be under both transcriptional and post-transcriptional control.
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Affiliation(s)
- Clifton K Fagerquist
- Produce Safety and Microbiology Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA,
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Silva CJ, Erickson-Beltran ML, Skinner CB, Dynin I, Hui C, Patfield SA, Carter JM, He X. Safe and Effective Means of Detecting and Quantitating Shiga-Like Toxins in Attomole Amounts. Anal Chem 2014; 86:4698-706. [DOI: 10.1021/ac402930r] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Christopher J. Silva
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Melissa L. Erickson-Beltran
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Craig B. Skinner
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Irina Dynin
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Colleen Hui
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Stephanie A. Patfield
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - John Mark Carter
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
| | - Xiaohua He
- Western Regional Research Center, United States Department of Agriculture, Albany, California 94710, United States
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18
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Top-down proteomic identification of Shiga toxin 2 subtypes from Shiga toxin-producing Escherichia coli by matrix-assisted laser desorption ionization-tandem time of flight mass spectrometry. Appl Environ Microbiol 2014; 80:2928-40. [PMID: 24584253 DOI: 10.1128/aem.04058-13] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We have analyzed 26 Shiga toxin-producing Escherichia coli (STEC) strains for Shiga toxin 2 (Stx2) production using matrix-assisted laser desorption ionization (MALDI)-tandem time of flight (TOF-TOF) tandem mass spectrometry (MS/MS) and top-down proteomic analysis. STEC strains were induced to overexpress Stx2 by overnight culturing on solid agar supplemented with either ciprofloxacin or mitomycin C. Harvested cells were lysed by bead beating, and unfractionated bacterial cell lysates were ionized by MALDI. The A2 fragment of the A subunit and the mature B subunit of Stx2 were analyzed by MS/MS. Sequence-specific fragment ions were used to identify amino acid subtypes of Stx2 using top-down proteomic analysis using software developed in-house at the U.S. Department of Agriculture (USDA). Stx2 subtypes (a, c, d, f, and g) were identified on the basis of the mass of the A2 fragment and the B subunit as well as from their sequence-specific fragment ions by MS/MS (postsource decay). Top-down proteomic identification was in agreement with DNA sequencing of the full Stx2 operon (stx2) for all strains. Top-down results were also compared to a bioassay using a Vero-d2EGFP cell line. Our results suggest that top-down proteomic identification is a rapid, highly specific technique for distinguishing Stx2 subtypes.
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Sandrin TR, Goldstein JE, Schumaker S. MALDI TOF MS profiling of bacteria at the strain level: a review. MASS SPECTROMETRY REVIEWS 2013; 32:188-217. [PMID: 22996584 DOI: 10.1002/mas.21359] [Citation(s) in RCA: 198] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 06/18/2012] [Accepted: 06/18/2012] [Indexed: 05/16/2023]
Abstract
Since the advent of the use of matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOF MS) as a tool for microbial characterization, efforts to increase the taxonomic resolution of the approach have been made. The rapidity and efficacy of the approach have suggested applications in counter-bioterrorism, prevention of food contamination, and monitoring the spread of antibiotic-resistant bacteria. Strain-level resolution has been reported with diverse bacteria, using library-based and bioinformatics-enabled approaches. Three types of characterization at the strain level have been reported: strain categorization, strain differentiation, and strain identification. Efforts to enhance the library-based approach have involved sample pre-treatment and data reduction strategies. Bioinformatics approaches have leveraged the ever-increasing amount of publicly available genomic and proteomic data to attain strain-level characterization. Bioinformatics-enabled strategies have facilitated strain characterization via intact biomarker identification, bottom-up, and top-down approaches. Rigorous quantitative and advanced statistical analyses have fostered success at the strain level with both approaches. Library-based approaches can be limited by effects of sample preparation and culture conditions on reproducibility, whereas bioinformatics-enabled approaches are typically limited to bacteria, for which genetic and/or proteomic data are available. Biological molecules other than proteins produced in strain-specific manners, including lipids and lipopeptides, might represent other avenues by which strain-level resolution might be attained. Immunological and lectin-based chemistries have shown promise to enhance sensitivity and specificity. Whereas the limits of the taxonomic resolution of MALDI TOF MS profiling of bacteria appears bacterium-specific, recent data suggest that these limits might not yet have been reached.
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Affiliation(s)
- Todd R Sandrin
- School of Mathematical and Natural Sciences, Arizona State University, Phoenix, Arizona 85069, USA.
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Boggess MV, Lippolis JD, Hurkman WJ, Fagerquist CK, Briggs SP, Gomes AV, Righetti PG, Bala K. The need for agriculture phenotyping: "moving from genotype to phenotype". J Proteomics 2013; 93:20-39. [PMID: 23563084 DOI: 10.1016/j.jprot.2013.03.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 03/12/2013] [Accepted: 03/19/2013] [Indexed: 11/28/2022]
Abstract
UNLABELLED Increase in the world population has called for the increased demand for agricultural productivity. Traditional methods to augment crop and animal production are facing exacerbating pressures in keeping up with population growth. This challenge has in turn led to the transformational change in the use of biotechnology tools to meet increased productivity for both plant and animal systems. Although many challenges exist, the use of proteomic techniques to understand agricultural problems is steadily increasing. This review discusses the impact of genomics, proteomics, metabolomics and phenotypes on plant, animal and bacterial systems to achieve global food security and safety and we highlight examples of intra and extra mural research work that is currently being done to increase agricultural productivity. BIOLOGICAL SIGNIFICANCE This review focuses on the global demand for increased agricultural productivity arising from population growth and how we can address this challenge using biotechnology. With a population well above seven billion humans, in a very unbalanced nutritional state (20% overweight, 20% risking starvation) drastic measures have to be taken at the political, infrastructure and scientific levels. While we cannot influence politics, it is our duty as scientists to see what can be done to feed humanity. Hence we highlight the transformational change in the use of biotechnology tools over traditional methods to increase agricultural productivity (plant and animal). Specifically, this review deals at length on how a three-pronged attack, namely combined genomics, proteomics and metabolomics, can help to ensure global food security and safety. This article is part of a Special Issue entitled: Translational Plant Proteomics.
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Affiliation(s)
- Mark V Boggess
- Agricultural Research Service, United States Department of Agriculture, Beltsville, MD, USA
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Fagerquist CK, Sultan O, Carter MQ. Possible evidence of amide bond formation between sinapinic acid and lysine-containing bacterial proteins by matrix-assisted laser desorption/ionization (MALDI) at 355 nm. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:2102-2114. [PMID: 23055076 DOI: 10.1007/s13361-012-0490-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 08/29/2012] [Accepted: 09/03/2012] [Indexed: 06/01/2023]
Abstract
We previously reported the apparent formation of matrix adducts of 3,5-dimethoxy-4-hydroxy-cinnamic acid (sinapinic acid or SA) via covalent attachment to disulfide bond-containing proteins (HdeA, Hde, and YbgS) from bacterial cell lysates ionized by matrix-assisted laser desorption/ionization (MALDI) time-of-flight-time-of-flight tandem mass spectrometry (TOF-TOF-MS/MS) and post-source decay (PSD). We also reported the absence of adduct formation when using α-cyano-4-hydroxycinnamic acid (CHCA) matrix. Further mass spectrometric analysis of disulfide-intact and disulfide-reduced over-expressed HdeA and HdeB proteins from lysates of gene-inserted E. coli plasmids suggests covalent attachment of SA occurs not at cysteine residues but at lysine residues. In this revised hypothesis, the attachment of SA is preceded by formation of a solid phase ammonium carboxylate salt between SA and accessible lysine residues of the protein during sample preparation under acidic conditions. Laser irradiation at 355 nm of the dried sample spot results in equilibrium retrogradation followed by nucleophilic attack by the amine group of lysine at the carbonyl group of SA and subsequent amide bond formation and loss of water. The absence of CHCA adducts suggests that the electron-withdrawing effect of the α-cyano group of this matrix may inhibit salt formation and/or amide bond formation. This revised hypothesis is supported by dissociative loss of SA (-224 Da) and the amide-bound SA (-206 Da) from SA-adducted HdeA and HdeB ions by MS/MS (PSD). It is proposed that cleavage of the amide-bound SA from the lysine side-chain occurs via rearrangement involving a pentacyclic transition state followed by hydrogen abstraction/migration and loss of 3-(4-hydroxy-3,5-dimethoxyphenyl)prop-2-ynal (-206 Da).
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Affiliation(s)
- Clifton K Fagerquist
- Agricultural Research Service, US Department of Agriculture, Western Regional Research Center, 800 Buchanan Street, Albany, CA 94710, USA.
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Stastna M, Van Eyk JE. Analysis of protein isoforms: can we do it better? Proteomics 2012; 12:2937-48. [PMID: 22888084 DOI: 10.1002/pmic.201200161] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 06/12/2012] [Accepted: 06/18/2012] [Indexed: 12/23/2022]
Abstract
Protein isoforms/splice variants can play important roles in various biological processes and can potentially be used as biomarkers or therapeutic targets/mediators. Thus, there is a need for efficient and, importantly, accurate methods to distinguish and quantify specific protein isoforms. Since protein isoforms can share a high percentage of amino acid sequence homology and dramatically differ in their cellular concentration, the task for accuracy and efficiency in methodology and instrumentation is challenging. The analysis of intact proteins has been perceived to provide a more accurate and complete result for isoform identification/quantification in comparison to analysis of the corresponding peptides that arise from protein enzymatic digestion. Recently, novel approaches have been explored and developed that can possess the accuracy and reliability important for protein isoform differentiation and isoform-specific peptide targeting. In this review, we discuss the recent development in methodology and instrumentation for enhanced detection of protein isoforms as well as the examples of their biological importance.
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Affiliation(s)
- Miroslava Stastna
- Johns Hopkins Bayview Proteomics Center, Department of Medicine, Division of Cardiology, School of Medicine, Johns Hopkins University, Baltimore, MD 21224, USA
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Fagerquist CK, Sultan O. A new calibrant for matrix-assisted laser desorption/ionization time-of-flight-time-of-flight post-source decay tandem mass spectrometry of non-digested proteins for top-down proteomic analysis. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2012; 26:1241-1248. [PMID: 22499200 DOI: 10.1002/rcm.6220] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
RATIONALE Matrix-assisted laser desorption/ionization (MALDI) time-of-flight-time-of-flight (TOF-TOF) post-source decay (PSD) tandem mass spectrometry (MS/MS) has seen increasing use for analysis of non-digested protein ions for top-down proteomic identification. However, there is no commonly accepted calibrant for this purpose beyond the use of peptide calibrants whose fragment ions span a lower mass-to-charge (m/z) range. METHODS We have used the PSD-generated fragment ions of disulfide-reduced/alkylated thioredoxin (AlkTrx) for TOF-TOF calibration in reflectron mode for the purpose of PSD-MS/MS analysis. The average m/z values of AlkTrx fragment ions were used for calibration. The quality of the calibration was assessed from the observed fragment ion mass error of MS/MS of the YahO protein from an unfractionated bacterial cell lysate of Escherichia coli O157:H7 as well as from MS/MS of bovine ubiquitin. The fragment ion mass errors of these two analytes were also used to assess instrument calibration using the monoisotopic fragment ions of [Glu(1)]-fibrinopeptide B (GluFib). RESULTS A general improvement in fragment ion mass accuracy was observed using the AlkTrx calibration compared to the GluFib calibration which resulted in a more significant top-down proteomic identification of these analyte proteins. CONCLUSIONS Our results suggest that AlkTrx may be useful as a calibrant for MALDI-TOF-TOF-PSD-MS/MS of small and modest-sized protein ions. The uniform fragmentation efficiency of YahO across its sequence suggests that it may be useful as a post-calibration standard to assess PSD-MS/MS instrument performance as well as establishing appropriate top-down proteomic fragment ion tolerances.
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Affiliation(s)
- Clifton K Fagerquist
- Western Regional Research Center, Agricultural Research Service, US Department of Agriculture, Albany, CA 94710, USA.
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Wang X, Zhang A, Sun H, Wu G, Sun W, Yan G. Network generation enhances interpretation of proteomics data sets by a combination of two-dimensional polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Analyst 2012; 137:4703-11. [DOI: 10.1039/c2an35891c] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Evolutionary silence of the acid chaperone protein HdeB in enterohemorrhagic Escherichia coli O157:H7. Appl Environ Microbiol 2011; 78:1004-14. [PMID: 22179243 DOI: 10.1128/aem.07033-11] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The periplasmic chaperones HdeA and HdeB are known to be important for cell survival at low pH (pH < 3) in Escherichia coli and Shigella spp. Here we investigated the roles of HdeA and HdeB in the survival of various enterohemorrhagic E. coli (EHEC) following exposure to pH 2.0. Similar to K-12 strains, the acid protections conferred by HdeA and HdeB in EHEC O145 were significant: loss of HdeA and HdeB led to over 100- to 1,000-fold reductions in acid survival, depending on the growth condition of prechallenge cells. However, this protection was much less in E. coli O157:H7 strains. Deletion of hdeB did not affect the acid survival of cells, and deletion of hdeA led to less than a 5-fold decrease in survival. Sequence analysis of the hdeAB operon revealed a point mutation at the putative start codon of the hdeB gene in all 26 E. coli O157:H7 strains analyzed, which shifted the ATG start codon to ATA. This mutation correlated with the lack of HdeB in E. coli O157:H7; however, the plasmid-borne O157-hdeB was able to restore partially the acid resistance in an E. coli O145ΔhdeAB mutant, suggesting the potential function of O157-HdeB as an acid chaperone. We conclude that E. coli O157:H7 strains have evolved acid survival strategies independent of the HdeA/B chaperones and are more acid resistant than nonpathogenic K-12 for cells grown under nonfavorable culturing conditions such as in Luria-Bertani no-salt broth at 28°C. These results suggest a divergent evolution of acid resistance mechanisms within E. coli.
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Top-down proteomic identification of furin-cleaved α-subunit of Shiga toxin 2 from Escherichia coli O157:H7 using MALDI-TOF-TOF-MS/MS. J Biomed Biotechnol 2011; 2010:123460. [PMID: 21331368 PMCID: PMC3038467 DOI: 10.1155/2010/123460] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 12/17/2010] [Indexed: 01/12/2023] Open
Abstract
A method has been developed to identify the α-subunit of Shiga toxin 2 (α-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 α-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 α-Stx2.
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