Lipoprotein receptors mediate cellular internalization of these particles and allow cells to acquire cholesterol and other lipids from outside. The main lipoprotein receptor is the apo B/E receptor synonymously known as the LDL receptor. This receptor was discovered by Goldstein and Brown, who jointly received the Nobel Prize for this work. As its name implies, it can bind either of the two apoproteins, apoE and apoB100. ApoE binds to LDL receptor with a higher affinity than apoB. The receptor gene is located on chromosome 19; the mature receptor protein is 839 amino acids long and spans the cell membrane (Fig. 17.4). The expression of the receptor gene is regulated by the intracellular cholesterol concentration.
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| ApoB48 cannot bind to the apoB/E receptor. The metabolism of chylomicron remnants is mediated by apoE binding primarily to the LDL receptor, but also to the LDL receptor-related protein (LRP).
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