Complete posttranslational modification mapping of pathogenic Neisseria meningitidis pilins requires top-down mass spectrometry

Authors

  • Joseph Gault,

    1. Structural Mass Spectrometry and Proteomics Unit, Institut Pasteur, CNRS UMR 3528, Paris, France
    2. Laboratoire des Mécanismes Réactionnels (DCMR), Département de Chimie, École Polytechnique, CNRS, Palaiseau, France
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  • Christian Malosse,

    1. Structural Mass Spectrometry and Proteomics Unit, Institut Pasteur, CNRS UMR 3528, Paris, France
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  • Silke Machata,

    1. INSERM U970, Paris Cardiovascular Research Center, Paris, France
    2. Université Paris Descartes, Faculté de Médecine Paris Descartes, Paris, France
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  • Corinne Millien,

    1. INSERM U970, Paris Cardiovascular Research Center, Paris, France
    2. Université Paris Descartes, Faculté de Médecine Paris Descartes, Paris, France
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  • Isabelle Podglajen,

    1. Service de Microbiologie, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges-Pompidou, Paris, France
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  • Marie-Cécile Ploy,

    1. INSERM UMR1092, Faculté de Médecine, Université de Limoges, Limoges, France
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  • Catherine E. Costello,

    1. Mass Spectrometry Resource, Department of Biochemistry, Boston University School of Medicine, Boston, MA, USA
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  • Guillaume Duménil,

    1. INSERM U970, Paris Cardiovascular Research Center, Paris, France
    2. Université Paris Descartes, Faculté de Médecine Paris Descartes, Paris, France
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  • Julia Chamot-Rooke

    Corresponding author
    1. Structural Mass Spectrometry and Proteomics Unit, Institut Pasteur, CNRS UMR 3528, Paris, France
    • Correspondence: Dr. Julia Chamot-Rooke, Structural Mass Spectrometry and Proteomics Unit, Institut Pasteur, CNRS UMR 3528, 26–28 Rue du Docteur Roux, 75724 Paris Cedex 15, France

      E-mail: julia.chamot-rooke@pasteur.fr

      Fax: +33-0-169334803

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  • Colour Online: See the article online to view Figs. 2 and 4 in colour.

Abstract

In pathogenic bacteria, posttranslationally modified proteins have been found to promote bacterial survival, replication, and evasion from the host immune system. In the human pathogen Neisseria meningitidis, the protein PilE (15–18 kDa) is the major building block of type IV pili, extracellular filamentous organelles that play a major role in mediating pathogenesis. Previous reports have shown that PilE can be expressed as a number of different proteoforms, each harboring its own set of PTMs and that specific proteoforms are key in promoting bacterial virulence. Efficient tools that allow complete PTM mapping of proteins involved in bacterial infection are therefore strongly needed. As we show in this study, a simple combination of mass profiling and bottom-up proteomics is fundamentally unable to achieve this goal when more than two proteoforms are present simultaneously. In a N. meningitidis strain isolated from a patient with meningitis, mass profiling revealed the presence of four major proteoforms of PilE, in a 1:1:1:1 ratio. Due to the complexity of the sample, a top-down approach was required to achieve complete PTM mapping for all four proteoforms, highlighting an unprecedented extent of glycosylation. Top-down MS therefore appears to be a promising tool for the analysis of highly posttranslationally modified proteins involved in bacterial virulence.

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