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Structural characterization of the inflammatory moiety of a variable major lipoprotein of Borrelia recurrentis
I G Scragg1, D Kwiatkowski, V Vidal
1University Department of Paediatrics, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
Abstract:
Louse-borne relapsing fever, caused by Borrelia recurrentis, provides one of the best documented examples of the causative role of tumor necrosis factor (TNF) in the pathology of severe infection in humans. We have identified the principal TNF-inducing factor of B. recurrentis as a variable major lipoprotein (Vmp). Here we report the complete gene sequence of Vmp, including its lipoprotein leader sequence. Using metabolically labeled forms of the native Vmp we confirm that the TNF inducing properties are associated with the lipid portion of the molecule. Quadrupole orthogonal time of flight mass spectrometry unequivocally locates the lipidic moiety at the NH(2)-terminal cysteine of the native polypeptide, and indicates the existence of three forms which are consistent with the structures C16:0, C16:0, C16:0 glyceryl cysteine; C18:1, C16:0, C16:0 glyceryl cysteine; and C18:0, C16:0, C16:0 glyceryl cysteine. These data provide the first direct evidence that the TNF inducing lipid modification of native Borrelia lipoproteins is a structural homologue of the murein lipoprotein of Escherichia coli.
Insights
The primary tumor necrosis factor (TNF)-inducing factor in Borrelia recurrentis, the cause of louse-borne relapsing fever, is a variable major lipoprotein (Vmp). Its lipid portion, specifically at the N-terminal cysteine, drives TNF induction, similar to E. coli
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Louse-borne relapsing fever, caused by Borrelia recurrentis, is a model for severe infection pathology.
- Tumor necrosis factor (TNF) plays a critical role in the human response to this infection.
Purpose of the Study:
- To identify and characterize the primary TNF-inducing factor of Borrelia recurrentis.
- To elucidate the molecular structure responsible for TNF induction.
Main Methods:
- Gene sequencing of the variable major lipoprotein (Vmp).
- Metabolic labeling of native Vmp.
- Quadrupole orthogonal time of flight mass spectrometry to determine lipid structure and location.
Main Results:
- The complete gene sequence of Vmp, including its leader sequence, was determined.
- TNF-inducing properties were confirmed to be associated with the lipid portion of Vmp.
- Mass spectrometry identified three distinct lipid structures at the N-terminal cysteine, homologous to E. coli murein lipoprotein.
Conclusions:
- The variable major lipoprotein (Vmp) is the principal TNF-inducing factor of Borrelia recurrentis.
- The lipid moiety at the N-terminal cysteine is responsible for TNF induction.
- This lipid modification is a structural homologue to that found in Escherichia coli murein lipoprotein.