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Updated: May 22, 2026
Applying Live Cell Imaging and Cryo-Electron Tomography to Resolve Spatiotemporal Features of the Legionella pneumophila Dot/Icm Secretion System
Published on: March 10, 2020
Highly sensitive quenched fluorescent substrate of Legionella major secretory protein (msp) based on its structural
Hervé Poras1, Sophie Duquesnoy, Emilie Dange
1Pharmaleads, Paris BioPark, 11 Rue Watt 75013 Paris, France. herve.poras@pharmaleads.com
Abstract:
Legionella pneumophila has been shown to secrete a protease termed major secretory protein (Msp). This protease belongs to the M4 family of metalloproteases and shares 62.9% sequence similarity with pseudolysin (EC 3.4.24.26). With the aim of developing a specific enzymatic assay for the detection and quantification of Msp, the Fluofast substrate library was screened using both enzymes in parallel. Moreover, based on the crystal structure of pseudolysin, a model of the Msp structure was built. Screening of the peptide library identified a lead substrate specifically cleaved by Msp that was subsequently optimized by rational design. The proposed model for Msp is consistent with the enzymatic characteristics of the studied peptide substrates and provides new structural information useful for the characterization of the protease. This study leads to the identification of the first selective and high affinity substrate for Msp that is able to detect picomolar concentrations of the purified enzyme. The identified substrate could be useful for the development of a novel method for the rapid detection of Legionella.
Insights
Researchers developed a novel assay to detect Legionella bacteria. A highly selective substrate was identified to quantify the major secretory protein (Msp), enabling picomolar detection for rapid Legionella identification.
Area of Science:
- Microbiology
- Enzymology
- Structural Biology
Background:
- Legionella pneumophila secretes a metalloprotease, major secretory protein (Msp), belonging to the M4 family.
- Msp shares significant sequence similarity with pseudolysin (EC 3.4.24.26).
Purpose of the Study:
- To develop a specific enzymatic assay for Msp detection and quantification.
- To characterize Msp structure and function.
Main Methods:
- Screening of the Fluofast substrate library using Msp and pseudolysin.
- Building a structural model of Msp based on pseudolysin's crystal structure.
- Rational design for optimizing a lead Msp substrate.
Main Results:
- Identification of the first selective, high-affinity substrate for Msp.
- The substrate enables detection of picomolar concentrations of purified Msp.
- A structural model consistent with enzymatic activity was proposed.
Conclusions:
- The identified substrate is crucial for developing rapid Legionella detection methods.
- New structural insights into Msp protease were gained.
- This work facilitates novel diagnostic tools for Legionella infections.
