GLYCOSYL INOSITOLPHOSPHOLIPID-ANCHORED STRUCTURES IN HERPETOMONAS-DAVIDI

Glycosyl inositolphospholipid (GPI)-anchored structures in the monogen etic parasite Herpetomonas davidi, were labeled with [H-3]myristic aci d and [H-3]glucosamine, and characterized by enzymatic and chemical tr eatments that are typical for the identification of GPI anchors. [H-3] Myristate incorporated into two different pools of GPI-linked structur es that could be separated by chromatography on octyl-Sepharose. One p ool consisted of three GPI-anchored proteins with apparent molecular m asses of 21, 31 and 45 kDa, and the GPI lipid moieties were identified as alkyl-lyso-glycerols. The label in the other pool associated with lipopeptidophosphoglycan (LPPG)-like structures of approximately 12-kD a molecular mass, containing ceramide-type GPI lipid anchors. While pr otein GPI anchors could also be labeled using [H-3]glucosamine as radi olabeled GPI anchor precursor, hardly any radioactivity was incorporat ed into the LPPG-like structures. H. davidi is one of the few organism s identified to date that synthesizes two structurally different lipid moieties for GPI anchoring of membrane components.