NOVEL GPI STRUCTURES OF THE MEMBRANE ANCHOR OF ACETYLCHOLINESTERASE FROM THE ELECTRIC ORGAN OF TORPEDO-CALIFORNICA

The structure of the glycan moiety of the glycosylphosphatidylinositol (GPI) membrane anchor from Torpedo californica electric organ acetylc holinesterase was solved using nuclear magnetic resonance (NMR), methy lation analysis, and chemical and enzymic microsequencing. Two structu res were found to be present: Glc alpha 1-2 Man alpha 1-2 Man alpha 1- 6 Man alpha 1-4 GlcN alpha 1-6myo-inositol, and Glc alpha 1-2 Man alph a 1-2 Man alpha 1-6 (GalNAc beta 1-4) Man alpha 1-4 GlcN alpha 1-6myo- inositol. The presence of glucose in this GPI anchor structure is a no vel feature. The anchor was also shown to contain 2.3 residues of etha nolamine per molecule.