Skip to content
Login Register

#lipid-linked proteins

2 public questions tagged with this topic.

Lipid Link Protein

Which is not a function of lipid-linked proteins?

Functional spectrum of lipid-linked proteins encompasses dynamic localization and signal integration far beyond simple tethering. N-myristoylated and palmitoylated kinases like Src family and non-receptor tyrosine kinases concentrate at inner leaflet raft domains upon growth factor stimulation scaffolding MAPK, PI3K pathways regulating proliferation and cytoskeletal remodeling. Small GTPases Ras Rab and Arf require prenylation plus secondary palmitoylation for vesicular transport from endoplasmic reticulum through Golgi to plasma membrane controlling vesicle budding and fusion. GPI anchors of hydrolytic enzymes ecto-5 prime nucleotidase and alkaline phosphatase provide apical sorting in polarized epithelia, high mobility for substrate encounter, and release by phospholipase for soluble enzyme generation. Structural roles include linking extracellular matrix. Passive diffusion across bilayers however occurs through solubility of small nonpolar molecules like O2 CO2 or via aqueous channels porins aquaporins and carriers exchanging down gradient driven by concentration. Lipid anchors do not generate aqueous pores therefore cannot mediate passive diffusion requiring channel proteins with selectivity filters.

Ref: Bhatnagar and Gordon, Understanding Protein Lipidation, J Cell Biol Reviews.

View Details
Lipid Link Protein

Which of the following statements about lipid-linked proteins is true?

Lipid-linked proteins associate with membranes via covalent attachment of hydrophobic moieties rather than simple non-specific interactions. Several distinct modifications exist: N-myristoylation adds 14-carbon myristate to N-terminal glycine after methionine removal via amide linkage, palmitoylation S-acylates internal cysteine via thioester that is reversible, prenylation attaches 15-carbon farnesyl or 20-carbon geranylgeranyl to C-terminal cysteine in CAAX motif via thioether, and glycosylphosphatidylinositol anchor attaches to C-terminus via phosphoethanolamine bridging to glycan core terminated by phosphatidylinositol lipid inserting into outer leaflet. GPI anchoring provides stable extracellular membrane tethering for enzymes like alkaline phosphatase and adhesion molecules like CD59 complement regulator, conferring localization to lipid rafts and enabling regulated release via phospholipases. Contrary to notion of only extracellular occurrence without post-translational processing, lipidation occurs co- or post-translationally in cytoplasm, endoplasmic reticulum and Golgi and determines membrane targeting and signaling localization. Such detailed mechanistic insight is frequently examined in competitive tests including NEET, CUET, CSIR-NET and GATE where transporter classification, energetics and disease linkage are integrated into problem-solving questions.

Ref: Resh, Nat Chem Biol 2013, Lipid modifications; Fujita et al., J Lipid Res 2020, GPI anchors.

View Details