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#protein anchoring

3 public questions tagged with this topic.

Glycolipid and Phospholipid

What is the primary function of glycosylphosphatidylinositol (GPI) anchors?

GPI anchoring represents post translational modification replacing C terminal transmembrane domain with glycolipid tether enabling raft association regulated release and apical sorting. Synthesis begins ER cytoplasmic leaflet adding GlcNAc phosphatidylinositol, deacetylation, flipping lumen, mannose three additions PIGM PIGB PIGV, phosphoethanolamine PIGN PIGO, attachment protein by transamidase complex PIGK GAA1 PIGS PIGT PIGU removing C terminal signal peptide forming amide bond ethanolamine phosphate mannose. Fatty acid remodeling PGAP1 PGAP3 generates saturated chains favoring ordered doma

Ref: Kinoshita T., Biochim Biophys Acta 2020, GPI anchor biosynthesis protein tethering raft.

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Plasma Membrane Proteins

Which type of membrane protein is covalently linked to a lipid moiety, anchoring it to the membrane?

Lipid linkage expands repertoire of membrane association beyond hydrophobic transmembrane spans enabling reversible targeting. Four major classes documented: N-myristoylation fourteen-carbon saturated fatty acid amide linked to N-terminal glycine after methionine removal catalyzed by N-myristoyltransferase cotranslationally; S-palmitoylation sixteen-carbon palmitate thioester linked to cysteine catalyzed by DHHC palmitoyl acyltransferases reversible by thioesterases controlling trafficking; prenylation fifteen-carbon farnesyl or twenty-carbon geranylgeranyl thioether linked to C-terminal CAAX

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 10, Lipid-Anchored Membrane Proteins.

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Lipid Link Protein

Which of the following statements is true regarding GPI-anchored proteins?

Glycosylphosphatidylinositol anchored proteins are synthesized in endoplasmic reticulum via en bloc transfer of preassembled GPI moiety to C-terminus after cleavage of hydrophobic signal, trafficked through Golgi where lipid remodeling occurs, and delivered to extracellular leaflet of plasma membrane where they reside in ordered lipid rafts enriched in cholesterol and sphingolipid. Attachment chemistry involves phosphoethanolamine bridging peptide carboxyl to glycan tetramannosyl glucosamine core linked via phosphodiester to phosphatidylinositol lipid with two fatty acyl chains inserted into o

Ref: Kinoshita & Fujita, Biochim Biophys Acta 2016, GPI-anchored proteins localization and bonds.

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