Lipoarabinomannan. Multiglycosylated form of the mycobacterial mannosylphosphatidylinositols.
The lipopolysaccharides of mycobacteria, lipoarabinomannan (LAM) and lipomannan (LM), of key importance in host-pathogen interaction, were recently shown to contain a phosphatidylinositol "anchoring domain." We now have established that LAM and LM are based on the phosphatidylinositol mannosides, the characteristic glycophospholipids of mycobacteria. Digestion of the arabinose-free LM with an endo-alpha 1----6-mannosidase yielded evidence for the presence of the 1-(sn-glycerol-3-phospho)-D-myo-inositol-2,6-bis-alpha-D-mannopyranoside unit, indistinguishable from that derived from phosphatidylinositol dimannoside. This same inositol substitution pattern was shown to be present in LAM by methylation analysis before and after dephosphorylation. Positions C-2 and C-6 of the inositol unit of LAM are occupied by mannosyl residues and C-1 by a phosphoryl group. Partial acid hydrolysis of per-O-methylated LAM and comparison by gas chromatography-mass spectrometry of the resulting derivatized oligosaccharides with like products from phosphatidylinositol hexamannoside demonstrated that the C-6 of inositol is the point of attachment of the mannan core of LAM, which consists of an alpha 1----6-linked backbone with considerable alpha-1----2 side chains. Thus, a structural and presumably biosynthetic relationship is established between some of the membranous mannosylphosphatidylinositols described some 25 years ago and the newly emerging, biologically active lipopolysaccharides of mycobacteria.
Chatterjee
D
D
Department of Microbiology, Colorado State University, Fort Collins 80523.
Hunter
S W
SW
McNeil
M
M
Brennan
P J
PJ
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D008401:Gas Chromatography-Mass Spectrometry; D006031:Glycosylation; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000302:isolation & purification; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009166:Mycobacterium leprae / Q000737:chemistry*; D009169:Mycobacterium tuberculosis / Q000737:chemistry*; D009844:Oligosaccharides / Q000737:chemistry / Q000302:isolation & purification; D010716:Phosphatidylinositols / Q000737:chemistry*
D008070:Lipopolysaccharides; D009844:Oligosaccharides; D010716:Phosphatidylinositols; C050016:lipoarabinomannan; C034154:phosphatidylinositol mannoside