STRUCTURAL STUDIES ON A LIPOARABINOGALACTAN OF CRITHIDIA-FASCICULATA

The monosaccharide D-arabinopyranose has only been found in glycoconju gates of the trypanosomatid parasites Leishmania major, Endotrypanum s chaudinni and Crithidia fasciculata. The donor molecule for the releva nt arabinosyltransferases is known to be GDP-alpha-D-Arap in L. major and C. fasciculata, and the latter organism is being used to study the biosynthesis of GDP-alpha-D-Arap. In this study, we describe the stru cture of the terminal product of arabinose metabolism in C. fasciculat a, namely lipoarabinogalactan. This molecule was purified by hydrophob ic-interaction chromatography and studied by a variety of techniques, including gas chromatography-mass spectrometry, electrospray mass spec trometry and chemical and enzymic digestions. These data show that lip oarabinogalactan contains a previously described D-arabino-D-galactan polysaccharide component covalently attached to a glycosylphosphatidyl inositol type of membrane anchor that is similar to, but not identical with, that found in the lipophosphoglycans of the Leishmania.