GPI anchor
Glycosylphosphatidylinositol anchor , GPI anchor for short , engl. GPI anchor , occur in all eukaryotic cells. Their main task is to anchor glycoproteins from the cell surface to the outside of the plasma membrane . The GPI anchor is attached to the terminal carboxy group of the glycoprotein in the lumen of the endoplasmic reticulum , whereby the signal sequence which coded for the import into the endoplasmic reticulum is cut off. Since the GPI anchor only interacts with a monolipid layer of the biomembrane , an interaction on the other side of the double membrane is prevented and contributes to the asymmetrical protein composition of the double membrane.
GPI anchors also lead to increased mobility of some proteins on the membrane and support signal transmission and cellular transport. In addition, they play an important role in the formation of antigens on the plasma membrane and thus lead to the identification of the cell.
The parasite Trypanosoma brucei cannot be recognized by the host's immune system due to its variable membrane proteins (variant surface glycoproteins, VSG), which can be made possible by the so-called VSG-GPI anchors.
GPI-anchored proteins could be detected by a phospholipase , which specifically cleaves inositol-containing phospholipids.
It was also proven that GPI anchors have a trimannose-glucosamine-inositol backbone.
literature
- Isabelle Flury: Glycosylphosphatidylinositol Membrane Anchors in Saccharomyces cerevisiae: Characterization of Proteins Involved in Side Chain Modifications. (PDF; 5.9 MB), dissertation. University of Friborg in Switzerland, 2001.
Individual evidence
- ↑ Gerald Karp, Kurt Begin: Molecular Cell Biology. Springer, 2005, ISBN 3-540-27466-9 , pp. 157-230.