REFINED STRUCTURE OF THE LIPOPHOSPHOGLYCAN OF LEISHMANIA-DONOVANI

The primary structure of the major surface glycoconjugate of Leishmani a donovani parasites, a lipophosphoglycan, has been further characteri zed. The repeating PO4-6Galp-beta-1-4Man disaccharide units, which are a salient feature of the molecule, are shown to terminate with one of several neutral structures, the most abundant of which is the branche d trisaccharide Galp-beta-1-4(Manp-alpha-1-2)Man. The phosphosaccharid e core of lipophosphoglycan, which links the disaccharide repeats to a lipid anchor, contains 2 phosphate residues. One of the core phosphat es has previously been localized on O-6 of the galactosyl residue dist al to the lipid anchor; the second phosphate is now shown to be on O-6 of the mannosyl residue distal to the anchor and to bear an alpha-lin ked glucopyranosyl residue. Also, the anomeric configuration of the un usual 3-substituted Galf residue in the phosphosaccharide core is esta blished as beta. The complete structure of the core is thus 1-PO4-6]Ma np-alpha-1-3Manp-alpha-1-4GlcN-alpha-1-. This further clarification of the structure of lipophosphoglycan may prove beneficial in determinin g the structure-function relationships of this highly unusual glycocon jugate.