Help! Not understanding completely. .) The lipid raft would be less stableor eve

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Help! Not understanding completely. .) The lipid raft would be less stableor even disappear) An increase in membrane fluidity of the lipid raft . A decrease in membrane fluidity of the lipid raft Proteins are present in all parts of the membrane, but some inte s seem to be associated with lipid rafts in particular cell types. For instance, the linker for activation of T-cells (LAT) is associated with rafts in certain T-cell gral membrane protein, populations. This change in lipid:protein ratio leads to a change in the mobility of lipid rafts during ultracentrifugation a detergents. In these experiments, lipid rafts are located in more buoyant fractions (higher t -280,000 x g following disruption of the cell with specific in the centrifuge tube) indicating a difference in density compared to other membrane regions (located to the bottom of the tube). In the following experiments, investigators looked at the role of cytoskeletal proteins in lipid raft formation. They applied colchicin (Colch; a microtubule inhibitor) or cytochalsin- D (CD; an actin filament inhibitor) to T-cells and then isolated lipids using detergent and ultracentrifugation as described above. Fractions were numbered from 1 (top of the centrifuge tube) to 12 (bottom of the centrifuge tube). A western blot was performed to look for the presence of LAT in separated lipid fractions. LAT is a protein "marker" for lipid raft formation in T-cells. In the control (untreated cells), LAT is found in buoyant fractions, which is indicative of lipid raft formation. A) Control LAT 4 5 6 7 89 10 11 12 B) Colch 4 5 67 89 10 11 12 C) CD LAT Modified from Head et al. (2006) J E 4 5 6 7 8 9 10 11 12

Explanation / Answer

LAT is a protein and is associated with rafts
Lipid raft located in higher in centrifuge tube when it occurs normally in the T cells.
In colchicin and Cytochalisn D inhibit the formation of LAT formation in T cells.

5. C- The cytoskeleton is required for lipid rafy formation.

6. LAT is no longer associated with lipid raft in the centrifuge gradient.

7. LAT localization to lipid rafts depends on an intact cytoskletal network
Lipid raft formation is required for stabilization of LAT.

8. A. Apply cytoskletal inhibitor and look for the presence of LAT in buoyant fractions.

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