Role
of a-hydroxylation
The presence of an alpha-OH group in the acyl chain of
the ceramide backbone of GalCer allows the formation of a H-bond network
which orientates the galactose ring of GalCer so that the molecule adopts
a typical L-shape structure (8). Consequently,
the sugar head of the glycosphingolipid is available for a stacking
interaction with exogenous ligands. In contrast, the galactose ring
of GalCer containing a nonhydroxylated acyl chain protrudes at 180¡
with respect to the plane of the membrane. For this reason, microbial
adhesins and/or toxins often recognize alpha-hydroxylated vs. nonhydroxylated
galactose-containing glycosphingolipids (9-13) : e.g. HIV1 surface envelope glycoprotein gp120,
infectious prion rods and Helicobacter pylori adhesins. |