Discription：ApoE is a major protein component of serum LDL, VLDL, HDL, and chylomicrons. It is produced predominantly by hepatocytes, macrophages, and nonneuronal cells in the CNS. ApoEcontaining particles transport triglycerides and cholesterol to peripheral tissues for cellular uptake and catabolism. Mature human ApoE is a 34kDa glycoprotein that consists of an Nterminal domain composed of four bundled αhelices, plus a hinge region and an extended αhelical C-terminal domain. Its amphipathic nature and flexible structure enable it to adopt dramatically different conformations upon lipid association. ApoE is monomeric in lipid particle, although it forms Homotetramer when lipid free.Mature human ApoE shares 71％ aa sequence identity with mouse and rat ApoE. ApoE is an important constituent of all plasma lipoproteins. Its interaction with specific ApoE receptor enables uptake of chylomicron remnants by liver cells, which is an essential step during normal lipid metabolism. It also binds with the LDL receptor （apo B/E） . Defects in ApoE are a cause of hyperlipoproteinemia type III. ApoE exists in three major isoforms; E2, E3, and E4, which differ from one another by a single amino-acid substitution. E3 is the most common isoform and is present in 40-90％ of the population. Recombinant Human ApoE3 is a 34.2kDa protein containing 299 amino acid residues.
