title: Inositol phosphate capping of the nonreducing termini of lipoarabinomannan from rapidly growing strains of Mycobacterium.
abstract: Previous studies have demonstrated that the nonreducing termini of the lipoarabinomannan (LAM) from Mycobacterium tuberculosis are extensively capped with mannose residues, whereas those from a fast growing Mycobacterium sp., once thought to be an attenuated strain of M. tuberculosis, are not. The noncapped LAM, termed AraLAM, is known to be more potent than the mannose-capped LAM (ManLAM) in inducing functions associated with macrophage activation. Using a combination of chemical and enzymatic approaches coupled with fast atom bombardment-mass spectrometry analysis, we demonstrated that LAMs from all M. tuberculosis strains examined (Erdman, H37Ra, and H37Rv), as well as the attenuated Mycobacterium bovis BCG strain, are mannose-capped with the extent of capping varying between 40 and 70%. The nonreducing termini of LAM from Mycobacterium leprae were also found to be capped with mannoses but at a significantly lower level. A novel inositol phosphate capping motif was identified on a minor portion of the otherwise uncapped arabinan termini of LAMs from the fast growing Mycobacterium sp. and Mycobacterium smegmatis ATCC 14468 and mc(2)155. In addition, an inositol phosphate tetra-arabinoside was isolated from among endoarabinase digestion products of AraLAM and was shown to induce tumor necrosis factor-alpha production. Accordingly, we concluded that AraLAM is characteristic of some rapidly growing Mycobacterium spp. It is distinct from ManLAMs of M. tuberculosis, M. bovis BCG, and Mycobacterium leprae not only in the absence of mannose-capping but also in containing some terminal inositol phosphate substituents which may account for its particular potency in inducing macrophage activation.
authors.affiliation: Department of Microbiology, Colorado State University, Fort Collins 80523, USA.
authors.forename: K H
authors.initials: KH
authors.lastname: Khoo
authors.forename: A
authors.initials: A
authors.lastname: Dell
authors.forename: H R
authors.initials: HR
authors.lastname: Morris
authors.forename: P J
authors.initials: PJ
authors.lastname: Brennan
authors.forename: D
authors.initials: D
authors.lastname: Chatterjee
mesh_terms: D000942:Antigens, Bacterial / Q000737:chemistry* / Q000378:metabolism; D001089:Arabinose / Q000737:chemistry; D002240:Carbohydrate Sequence; D017666:Deuterium Oxide; D006868:Hydrolysis; D007295:Inositol Phosphates / Q000032:analysis* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000378:metabolism; D008358:Mannose / Q000737:chemistry; D008969:Molecular Sequence Data; D009161:Mycobacterium / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism; D009163:Mycobacterium bovis / Q000737:chemistry; D009166:Mycobacterium leprae / Q000737:chemistry; D009169:Mycobacterium tuberculosis / Q000737:chemistry; D010084:Oxidation-Reduction; D013045:Species Specificity; D016339:Spectrometry, Mass, Fast Atom Bombardment
chemical_list: D000942:Antigens, Bacterial; D007295:Inositol Phosphates; D008070:Lipopolysaccharides; C050016:lipoarabinomannan; D001089:Arabinose; D017666:Deuterium Oxide; D008358:Mannose