Application

Apolipoprotein A-I from human plasma has been used to induce cholesterol efflux in nitrobenzoxadiazole (NBD)-cholesterol loaded cells. It has also been used to detect IgG anti-apoA-1 antibodies using enzyme linked immunosorbent assay (ELISA).

Major protein components in high density lipoprotein (HDL)

Biochem/physiol Actions

Apo-AI comprises ~70% of the protein moiety in HDL. It is a single polypeptide chain consisting of 245 amino acids with glutamic acid as the C-terminal residue and aspartic acid as the N-terminal residue. The molecular mass is reported to be 28.3 kDa. The protein is made up of one major isoform (pI 5.6) and two minor isoforms (pI 5.53 and 5.46). Apo-AI shows a high content of α-helix structure. The amphipathic regions in the α-helix structure seem to be responsible for lipid binding capacity. In aqueous solution, Apo-AI shows self-association with minor conformation change. Apo-AI activates lecithin-cholesterol (LCAT) acyltransferase, which is responsible for cholesterol esterification in plasma.Apo-AI levels in normal plasma are 90-130 mg/dl. Apo-AI levels may be inversely related to the risk of coronary disease.

Physical form

Solution in 10 mM ammonium bicarbonate