APOLIPOPROTEIN OF HIGH DENSITY LIPOPROTEIN

Apolipoprotein A-I is the major apoprotein of High Density Lipoprotein and is a relatively abundant plasma protein with a concentration of 1.0-1.5 mg/ml. It is a single polypeptide chain with 243 amino acid residues of known primary amino acid sequence (Brewer et al., 1978). Apolipoprotein A-I is a cofactor for LCAT (606967), which is responsible for the formation of most cholesteryl esters in plasma. apoA-I also promotes efflux of cholesterol from cells. The liver and small intestine are the sites of synthesis of apoA-I . The primary translation product of the APOA1 gene contains both a pre and a pro segment, and posttranslational processing of apoA-I may be involved in the formation of the functional plasma apoA-I isoproteins. Dayhoff (1976) pointed to sequence homologies of A-I, A-II , C-I , and C-III .

Apo A-I is a peptide of molecular weight 28,300 that is a major component of HDLs and is also found in chylomicrons .