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. 2020 Nov 17;11:611188. doi: 10.3389/fpls.2020.611188

Figure 1.

Figure 1

(A) Structure of the conserved glycosylphosphatidylinositol (GPI)-anchor backbone. (B) Biosynthesis of plant GPI precursor in the endoplasmic reticulum (ER). The biosynthesis is a stepwise process initiated at the cytoplasmic side of the ER by the GPI-GlcNAc-transferase (GPI-GnT) multiprotein complex (SETH1, SETH2, PIG-H, PIG-P, PIG-Q, PIG-Y, and DPM2). The GlcNAc is de-N-acetylated by PIG-L and GlcN-PI flips to the luminal side of the ER. GPI mannosyltransferases PNT1 (homolog of mammalian PIG-M), PIG-V and ATPG1 (homolog of mammalian PIG-B) attach the three mannose (Man) residues to the backbone, which is further modified by attachment of ethanolamine phosphate (EtNP). The assembled precursor is transferred en bloc by the GPI transamidase complex (PIG-K, GPAA1, PIG-S, PIG-T, and PIG-U) to proteins. In addition to the bridging EtNP, one or two additional EtNP may be transferred to mannose residues by specific GPI-EtNP transferases that are present in Arabidopsis thaliana (Ellis et al., 2010; Luschnig and Seifert, 2011).