Figure 1: Cycling lipid transport. | Nature

Figure 1: Cycling lipid transport.

From: Countercurrents in lipid flow

Figure 1

Two studies1,2 describe how members of the OSBP protein family move the lipid phosphatidylserine (PS) from its site of synthesis in a cellular organelle called the endoplasmic reticulum (ER) to the inner surface of the plasma membrane, where it becomes enriched. The OSBP-related protein (ORP5 or ORP8 in mammals, Osh6 or Osh7 in yeast) binds PS and another lipid, phosphatidylinositol-4-phosphate (PI4P), in a mutually exclusive fashion. a, PS is picked up at the ER and offloaded at the plasma membrane, in exchange for PI4P. b, PI4P is delivered to the ER, where the phosphatase enzyme Sac1 hydrolyses it to phosphatidylinositol (PI). The cycle is maintained through the continual resynthesis of PI4P from PI at the plasma membrane.

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