Interaction of the GM2 activator protein with sulfated and sialylated glycosphingolipids.

Publisher Summary This chapter investigates the interaction of the G M2 activator protein with sulfated and sialylated glycosphingolipids. Data concerning the interaction of G M2 AP with gangliosides were obtained from biophysical measurements. The membrane activity of G M2 AP was measured by high-sensitivity differential scanning calorimetry (DSC) and film balance measurements, as well as by surface plasmoresonance studies. Analytical techniques such as thin-layer chromatography (TLC) overlay and fluorescence dequenching techniques provided evidence for the specific interaction between the lipid-binding protein and gangliosides. By TLC overlay it was shown that G M2 AP bound to G M1 , the precursor of G M2 in ganglioside catabolism; G M2 itself; and G M3 , the product of G M2 degradation. In vivo , the G M2 AP is required for the degradation of ganglioside G M2 and glycolipid GA2, as well as for the sufficient degradation of glycolipid S M2 a. In vitro it also acts on related GSL, such as G M1 or globotetraosylceramide. Binding and transfer studies suggested that this cofactor acts as a liftase, –it recognizes its lipid substrate, complexes it, and lifts it out of the membrane plane, thus presenting it to the water-soluble enzyme for degradation.