Structural characterization of the inflammatory moiety of a variable majorlipoprotein of Borrelia recurrentis

Louse-borne relapsing fever, caused by Borrelia recurrentis, provides one o f the best documented examples of the causative role of tumor necrosis fact or (TNF) in the pathology of severe infection in humans, We have identified the principal TNF-inducing factor of B. recurrentis as a variable major li poprotein (Vmp), Here we report the complete gene sequence of Vmp, includin g 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 ma ss spectrometry unequivocally locates the lipidic moiety at the NH2-termina l 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 g lyceryl cysteine, These data provide the first direct evidence that the TNF inducing lipid modification of native Borrelia lipoproteins is a structura l homologue of the murein lipoprotein of Escherichia coli.