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Updated: Mar 6, 2026
Crystallization of Membrane Proteins in Lipidic Mesophases
Published on: March 28, 2011
Crystallization of FcpA from Leptospira, a novel flagellar protein that is essential for pathogenesis
Fabiana San Martin1, Ariel E Mechaly1, Nicole Larrieux1
1Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, 11400 Montevideo, Uruguay.
Abstract:
The protein FcpA is a unique component of the flagellar filament of spirochete bacteria belonging to the genus Leptospira. Although it plays an essential role in translational motility and pathogenicity, no structures of FcpA homologues are currently available in the PDB. Its three-dimensional structure will unveil the novel motility mechanisms that render pathogenic Leptospira particularly efficient at invading and disseminating within their hosts, causing leptospirosis in humans and animals. FcpA from L. interrogans was purified and crystallized, but despite laborious attempts no useful X ray diffraction data could be obtained. This challenge was solved by expressing a close orthologue from the related saprophytic species L. biflexa. Three different crystal forms were obtained: a primitive and a centred monoclinic form, as well as a hexagonal variant. All forms diffracted X-rays to suitable resolutions for crystallographic analyses, with the hexagonal type typically reaching the highest limits of 2.0 Å and better. A variation of the quick-soaking procedure resulted in an iodide derivative that was instrumental for single-wavelength anomalous diffraction methods.
Insights
Structural insights into the bacterial flagellar protein FcpA were obtained by crystallizing an orthologue from Leptospira biflexa. This breakthrough reveals novel mechanisms of spirochete motility and pathogenicity.
Area of Science:
- Structural Biology
- Microbiology
- Biochemistry
Background:
- The flagellar protein FcpA is crucial for motility and pathogenicity in Leptospira spirochetes.
- No 3D structures of FcpA homologues are available in the Protein Data Bank (PDB).
- Understanding FcpA structure is key to deciphering pathogenic Leptospira's invasion mechanisms.
Purpose of the Study:
- To determine the three-dimensional structure of FcpA.
- To provide insights into the novel motility mechanisms of pathogenic Leptospira.
- To facilitate the development of strategies against leptospirosis.
Main Methods:
- Expression and purification of an FcpA orthologue from Leptospira biflexa.
- Crystallization of the protein, yielding three distinct crystal forms (monoclinic and hexagonal).
- X-ray diffraction analysis, including single-wavelength anomalous diffraction (SAD) using an iodide derivative.
Main Results:
- Successfully obtained high-resolution X-ray diffraction data (2.0 Å and better) from hexagonal crystals.
- Determined the three-dimensional structure of the FcpA orthologue.
- Identified an iodide derivative suitable for SAD phasing.
Conclusions:
- The determined FcpA structure provides a foundation for understanding spirochete flagellar motility.
- This structural information can elucidate pathogenic mechanisms of Leptospira.
- The study overcomes previous challenges in obtaining structural data for FcpA homologues.
