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#lipid modification

6 public questions tagged with this topic.

Glycolipid and Phospholipid

Which lipid modification helps maintain membrane curvature?

Maintenance high curvature membranes such as thirty nanometer synaptic vesicles tubular ER sheets requires conical lipids complementing protein scaffolds BAR ENTH and reticulons. Phosphatidylethanolamine ethanolamine headgroup cross section smaller than diacylglycerol tail volume adopts molecular cone favoring negative mean curvature concave cytosolic leaflet facilitating fission fusion stalk formation hemifusion diaphragm expansion. Synthesis via Kennedy pathway CDP ethanolamine ethanolamine phosphotransferase EPT1 and mitochondrial phosphatidylserine decarboxylase PSD converting PS PE enrich

Ref: Vance JE & Tasseva G., Biochim Biophys Acta 2013, PE cone shape maintains curvature and fusion.

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Lipid Link Protein

Which lipid modification can be reversed by palmitoyl-protein thioesterase?

Palmitoylation also called S-acylation refers to attachment of 16-carbon saturated palmitate from palmitoyl-CoA to cysteine thiol via thioester bond catalyzed by membrane-bound DHHC motif palmitoyl acyltransferases containing Asp-His-His-Cys catalytic tetrad. Unlike myristoylation or prenylation irreversible thioether amide linkages, thioester is chemically labile and enzymatically reversible, providing dynamic regulation. Removal catalyzed by acyl protein thioesterases APT1 and APT2 and ABHD17 family depalmitoylases in cytosol and lysosomal palmitoyl-protein thioesterase PPT1 involved in Niem

Ref: Linder & Deschenes, Nat Rev Mol Cell Biol 2007, Palmitoylation regulation; Chamberlain & Shipston, Physiol Rev 2015.

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Lipid Link Protein

How many carbon atoms are present in the farnesyl lipid modification?

Prenylation adds isoprenoid lipids derived from mevalonate pathway to cysteine in CAAX motif. Two major forms exist: 15-carbon farnesyl comprising three isoprene units and 20-carbon geranylgeranyl comprising four isoprene units. Farnesyl pyrophosphate synthesized from isopentenyl pyrophosphate and dimethylallyl pyrophosphate serves donor for farnesyltransferase FTase, while geranylgeranyl pyrophosphate serves donor for geranylgeranyltransferase I and II. Farnesyl group contains 15 carbon atoms arranged as 2E,6E-farnesyl with three double bonds providing hydrophobic moiety about 10 angstrom len

Ref: Zhang & Casey, Annu Rev Biochem 1996, Prenyl groups; Wang & Casey 2016, Prenylation.

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Lipid Link Protein

Which statement is correct about farnesylation?

Farnesylation is post-translational prenylation catalyzed by heterodimeric farnesyltransferase FTase using farnesyl pyrophosphate derived from mevalonate cholesterol biosynthesis pathway as donor. Modification occurs at CAAX motif at extreme C-terminus where C is cysteine, A aliphatic residues, X typically methionine, serine or glutamine directing farnesyl addition versus leucine directing geranylgeranyl addition. Reaction forms thioether bond between cysteine sulfur and C1 of isoprenoid. Farnesyl group is linear 15-carbon isoprene polymer comprising three isoprene units with 3 double bonds pr

Ref: Zhang & Casey, Annu Rev Biochem 1996, Farnesylation; Wang & Casey 2016.

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Lipid Link Protein

Which of the following lipid modifications involves thioether bond formation?

Lipid modifications differ in chemistry of linkage and reversibility. N-myristoylation forms amide bond between myristate and N-terminal glycine co-translationally irreversible, palmitoylation forms thioester between 16-carbon palmitate and cysteine thiol reversibly cleaved by acyl protein thioesterases, GPI anchoring forms amide between ethanolamine phosphate and C-terminus plus glycosidic linkages to inositol phospholipid. Prenylation, either farnesylation 15-carbon or geranylgeranylation 20-carbon, occurs at C-terminal CAAX motif where X determines farnesyl vs geranylgeranyl transferase spe

Ref: Wang & Casey, Nat Rev Mol Cell Biol 2016, Protein prenylation and thioether linkage.

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Cell Signaling Dev Bio & Other Pathways

Wnt proteins are unusual because they are

Lipid-modified, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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