Hong Yeonchul, Nagamune Kisaburo, Ohishi Kazuhito, Morita Yasu S, Ashida Hisashi, Maeda Yusuke, Kinoshita Taroh
Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
FEBS Lett. 2006 Jan 23;580(2):603-6. doi: 10.1016/j.febslet.2005.12.075. Epub 2006 Jan 4.
Glycosylphosphatidylinositol (GPI) is widely used by eukaryotic cell surface proteins for membrane attachment. De novo synthesized GPI precursors are attached to proteins post-translationally by the enzyme complex, GPI transamidase. TbGPI16, a component of the trypanosome transamidase, shares similarity with human PIG-T. Here, we show that TbGPI16 is the orthologue of PIG-T and an essential component of GPI transamidase by creating a TbGPI16 knockout. TbGPI16 forms a disulfide-linked complex with TbGPI8. A cysteine to serine mutant of TbGPI16 was unable to fully restore the surface expression of GPI-anchored proteins upon transfection into the knockout cells, indicating that its disulfide linkage with TbGPI8 is important for the full transamidase activity.
