TY - JOUR
T1 - A novel glycosylphosphatidylinositol in African trypanosomes
T2 - A possible catabolic intermediate
AU - Milne, Kenneth G.
AU - Ferguson, Michael A.J.
AU - Englund, Paul T.
PY - 1999/1/15
Y1 - 1999/1/15
N2 - The major glycosylphosphatidylinositols (GPIs) in African trypanosomes are glycolipid A, the precursor of the variant surface glycoprotein membrane anchor, and glycolipid C, a species identical to glycolipid A except that it contains an acylated inositol. Both glycolipids A and C contain dimyristoyl glycerol and are efficiently labeled with [3H]myristate in a cell-free system. We now report a novel GPI known as lipid X. This GPI is radiolabeled strongly with [3H]palmitate (and very poorly with [3H]myristate or [3H]stearate) in digitonin-permeabilized cells. The structure of lipid X is Man1GlcNAc-(2-O-palmitoyl)-D-myo-inositol-1-HPO4-3(lyso-palmitoylglycerol). Metabolically, lipid X exists as an intermediate, and can be detected only under conditions in which its formation is stimulated (e.g. by EDTA) or its breakdown is inhibited (e.g. by Co2+). Lipid X has not been observed previously because these conditions do not support GPI biosynthesis. We speculate that lipid X is an intermediate in the catabolism of conventional trypanosome GPIs, possibly deriving from breakdown of glycolipid C.
AB - The major glycosylphosphatidylinositols (GPIs) in African trypanosomes are glycolipid A, the precursor of the variant surface glycoprotein membrane anchor, and glycolipid C, a species identical to glycolipid A except that it contains an acylated inositol. Both glycolipids A and C contain dimyristoyl glycerol and are efficiently labeled with [3H]myristate in a cell-free system. We now report a novel GPI known as lipid X. This GPI is radiolabeled strongly with [3H]palmitate (and very poorly with [3H]myristate or [3H]stearate) in digitonin-permeabilized cells. The structure of lipid X is Man1GlcNAc-(2-O-palmitoyl)-D-myo-inositol-1-HPO4-3(lyso-palmitoylglycerol). Metabolically, lipid X exists as an intermediate, and can be detected only under conditions in which its formation is stimulated (e.g. by EDTA) or its breakdown is inhibited (e.g. by Co2+). Lipid X has not been observed previously because these conditions do not support GPI biosynthesis. We speculate that lipid X is an intermediate in the catabolism of conventional trypanosome GPIs, possibly deriving from breakdown of glycolipid C.
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U2 - 10.1074/jbc.274.3.1465
DO - 10.1074/jbc.274.3.1465
M3 - Article
C2 - 9880521
AN - SCOPUS:0033555923
SN - 0021-9258
VL - 274
SP - 1465
EP - 1471
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 3
ER -