Characterization of lipophosphoglycan from a ricin-resistant mutant of Leishmania major.
One of the virulence factors of the protozoan parasite Leishmania major is the surface glycoconjugate, lipophosphoglycan (LPG). A Ricin-resistant mutant of L.major was generated and characterised with respect to its virulence in mice and the structure and expression of LPG. The LPG from this mutant (1F6-B5) retained the tripartite structure of wild-type LPG, comprising a glycosylphosphatidylinositol (GPI) anchor linked to a phosphorylated disaccharide backbone terminating in a nonreducing neutral oligosaccharide cap. The structure of the GPI anchor and the major capping oligosaccharide were identical to wild-type LPG. However, there were variations in the number of phosphorylated repeats (PO4-6Gal(beta 1-4)Man(alpha 1-) comprising the backbone of LPG, although the degree of substitution with side branches (approx. 95%) was similar to that of wild-type LPG. Thus, the mutant LPG was shorter in length having, on average, 15 repeat units per molecule compared with 30 in the wild-type LPG. The mutant LPG contained both arabinose (Ara(beta 1-2)[Gal(beta 1-3)-]1,2) and galactose ([Gal(beta 1-3)-]1-8) capped side branches linked to the backbone. In contrast to wild-type LPG, the number of arabinose-capped side chains was significantly reduced, and a new population of galactose-capped (Gal(beta 1-3)]5-8) side branches was present. The level of LPG expression in mutant parasites was approximately one-tenth of the wild-type parasite. The mutant parasites were avirulent in mice. Over a period of 18 months, they did not cause lesions and organisms could not be isolated from the draining lymph nodes.
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Walter and Eliza Hall Institute of Medical Research, Post Office Royal Melbourne Hospital, Victoria, Australia.
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Currie
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Handman
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Bacic
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D000818:Animals; D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D004351:Drug Resistance / Q000235:genetics; D005260:Female; D006028:Glycosphingolipids / Q000737:chemistry*; D018320:Leishmania major / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity; D013058:Mass Spectrometry; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D009154:Mutation; D012276:Ricin / Q000494:pharmacology*
D006028:Glycosphingolipids; C008290:lipophosphonoglycan; D012276:Ricin