Enriching Subcellular Proteins in Leptospira Using a Triton X-114-Based Fractionation Approach
August 8th, 2025
Though prokaryotes lack an organellar system, there are subcellular regions with localized proteins. Quantitative and qualitative analysis of the enzymes and proteins in the subcellular regions is important for developing drug and vaccine targets. Here, we illustrate the subcellular fractionation of Leptospiral proteins using Triton X-114 and its analysis.
We are isolating subcellular proteins in Leptospira to understand protein's localization, which helps in identifying virulence factors in pathogenic gram-negative bacteria. Subcellular proteomics now employs high-throughput mass spectrometry and optimize fractionation to dissect pathogen protein architecture with enhanced precision. An example is virulence factor detection. We use Triton-X-114 based separation, LCMS-MS, SDS-PAGE, and immunoblotting to extract and identify compartment-specific protein in bacteria. Maintaining protein integrity during extraction, detergent optimizations, and avoiding cross-contamination between cellular fractions remains key challenges. We aim to map dynamic changes in pathogenic bacteria proteome during infection, and try to find potential virulence factors.
[Narrator] To begin, grow Leptospira interrogans in Ellinghausen-McCullough Johnson Harris medium supplemented with 1% BSA. After seven days of incubation, the biological replicates of the Leptospira culture transfer into 50 milliliter centrifuge tubes. Centrifuge the tubes at 2,500 G for 45 minutes at four degrees Celsius. Decant the supernatant into a beaker containing disinfectant and discard it. Reserve the cell pellets for the next step. Wash each cell pellet three times with one milliliter of PBS supplemented with five millimolar magnesium chloride. After each wash, centrifuge at 10,000 G for 10 minutes at four degrees Celsius. Treat the harvested Leptospira cell pellet with one milliliter of extraction buffer. Below 25 degrees Celsius, gently mix the buffer with the pellet using a micropipette until the solution becomes visibly turbid. Incubate the mixture overnight at four degrees Celsius. After mixing the overnight incubated extract with a micropipette, centrifuge the mixture at 15,000 G for 30 minutes at four degrees Celsius. Carefully decant the supernatant into a clean vial and retain the cell pellet for the next step. Now, add 50 microliters of buffer containing protease inhibitor cocktail to the retained pellet. Vortex the tube continuously for five minutes, then incubate at four degrees Celsius for another five minutes. Then centrifuge the tube at 15,000 G for 30 minutes at four degrees Celsius. Now, adjust the Triton-X-114 concentration in the extracted supernatant to 2%. Incubate the mixture at 37 degrees Celsius for one hour, then centrifuge at 2,000 G for five minutes at 30 degrees Celsius to promote phase separation. Allow the mixture to settle for one minute to complete separation. To isolate the top aqueous phase, pierce the interface with a sterile syringe and transfer it to a vial.
SDS-PAGE, followed by immunoblotting, confirmed the presence of LipL41 protein in aqueous, detergent, and pellet fractions, indicating its distribution across all cellular compartments. FlaB protein was detected exclusively in the pellet fraction confirming its localization to the inner membrane associated paraplasmic space.
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Overview
This study focuses on isolating subcellular proteins in Leptospira to understand their localization, which aids in identifying virulence factors in pathogenic gram-negative bacteria. The research employs high-throughput mass spectrometry and optimized fractionation techniques to enhance the precision of pathogen protein analysis.
Key Study Components
Area of Science
- Microbiology
- Proteomics
- Pathogen Research
Background
- Prokaryotes lack an organellar system but have subcellular regions with localized proteins.
- Understanding protein localization is crucial for developing drug and vaccine targets.
- Subcellular proteomics is essential for dissecting pathogen protein architecture.
- Challenges include maintaining protein integrity and avoiding cross-contamination.
Purpose of Study
- To map dynamic changes in the proteome of pathogenic bacteria during infection.
- To identify potential virulence factors in Leptospira.
- To enhance the understanding of protein localization in bacteria.
Methods Used
- Isolation of Leptospira cells and centrifugation for pellet collection.
- Washing of cell pellets and treatment with extraction buffer.
- Use of Triton X-114 for phase separation of proteins.
- High-throughput mass spectrometry for protein identification.
Main Results
- Successful isolation of compartment-specific proteins from Leptospira.
- Identification of potential virulence factors through proteomic analysis.
- Demonstration of effective protein extraction and separation techniques.
- Insights into the dynamic changes in the bacterial proteome during infection.
Conclusions
- The study provides a framework for understanding protein localization in pathogenic bacteria.
- Identifying virulence factors can lead to better drug and vaccine development.
- Optimized methods enhance the accuracy of subcellular proteomic studies.
