Question

First, the group studied effect of ATP on flippase activity. Previous experiments have shown that incubating RBCs with iodoacetamide and inosine causes ATP levels to decrease to 60%. In Figure 5, RBCs was pre-treated with lodoacetamide and inosine for either 15 or 30 minutes, and then phospholipid vesicles containing purified DMPS were added. The control batch of RBCs was not treated with lodoacetamide and inosine. The results are shown in Figure Q2. Data analysis Figure 5 a. [SA] Describe and explain the results obtained based on what you know about flippase mechanism and activity. Figure 5. The effect of ATP depletion on red blood cell shape (MI). Solid triangles represent pre-treatment of red blood cells with lodoacetamide and Inosine for 15 minutes and solid squares for 30 minutes. The control (no pre-treatment) is represented by solid circles. Time is in b. [SA] Scramblases do not require ATP in order to allow lipids to move from one surface to the other. What is the difference between scramblase and flippase? Why is flippase activity ATP-dependent? hours. Experiments were conducted in order to determine which amino acid side chains in the flippase enzyme were essential to its translocation ability. RBCs were pretreated with diamide, a reagent that modifies sulfhydryl. After the pre-treatment, the researchers carried out the shape change experiment as usual. The results are shown in Figure 6. Figure 6. The effect of diamide treatment or DMPS-Induced red blood shape change (MI The solid triangles (top) represent cells pre treated with diamide and the solid circles represent the control cells (not pre-treated) Time is in hours. Q3. [SA] Data analysis Figure 6. Describe and explain the results obtained based on what you know about amino acids that have sulfhydryl groups.

Answer 1

Flippases translocate phospholipids from one side of a membrane to the other even against a gradient of concentration. Flipping of membrane embedded lipids containing large polar heads is a slow and energetically unfavourable process, the mechanism of which was until recently, largely unknown. This process is catalysed by transmembrane ATPases called flippases and is essential for maintaining membrane lipid asymmetry, signalling, vescile formation and regulation of membrane protein activity.