Distinct central amphipathic alpha-helices in apolipoprotein A-I contribute to the in vivo maturation of high density lipoprotein by either activating lecithin-cholesterol acyltransferase or binding lipids

J Biol Chem. 2000 Feb 18;275(7):5043-51. doi: 10.1074/jbc.275.7.5043.


Recombinant adenoviruses with cDNAs for human apolipoprotein A-I (wild type (wt) apoA-I) and three mutants, referred to as Delta4-5A-I, Delta5-6A-I, and Delta6-7A-I, that have deletions removing regions coding for amino acids 100-143, 122-165, and 144-186, respectively, were created to study structure/function relationships of apoA-I in vivo. All mutants were expressed at lower concentrations than wt apoA-I in plasma of fasting apoA-I-deficient mice. The Delta5-6A-I mutant was found primarily in the lipid-poor high density lipoprotein (HDL) pool and at lower concentrations than Delta4-5A-I and Delta6-7A-I that formed more buoyant HDL(2/3) particles. At an elevated adenovirus dose and earlier blood sampling from fed mice, both Delta5-6A-I and Delta6-7A-I increased HDL-free cholesterol and phospholipid but not cholesteryl ester. In contrast, wt apoA-I and Delta4-5A-I produced significant increases in HDL cholesteryl ester. Further analysis showed that Delta6-7A-I and native apoA-I could bind similar amounts of phospholipid and cholesterol that were reduced slightly for Delta5-6A-I and greatly for Delta4-5A-I. We conclude from these findings that amino acids (aa) 100-143, specifically helix 4 (aa 100-121), contributes to the maturation of HDL through a role in lipid binding and that the downstream sequence (aa 144-186) centered around helix 6 (aa 144-165) is responsible for the activation of lecithin-cholesterol acyltransferase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apolipoprotein A-I / chemistry
  • Apolipoprotein A-I / genetics
  • Apolipoprotein A-I / metabolism*
  • DNA, Complementary
  • Enzyme Activation
  • Humans
  • Lipid Metabolism*
  • Lipoproteins, HDL / genetics
  • Lipoproteins, HDL / metabolism*
  • Mice
  • Mutation
  • Phosphatidylcholine-Sterol O-Acyltransferase / metabolism*
  • Protein Conformation
  • Protein Processing, Post-Translational*
  • Sequence Deletion
  • Ultracentrifugation


  • Apolipoprotein A-I
  • DNA, Complementary
  • Lipoproteins, HDL
  • Phosphatidylcholine-Sterol O-Acyltransferase