The helix bundle: a reversible lipid binding motif

Comp Biochem Physiol A Mol Integr Physiol. 2010 Feb;155(2):123-33. doi: 10.1016/j.cbpa.2009.09.009. Epub 2009 Sep 19.


Apolipoproteins are the protein components of lipoproteins that have the innate ability to inter convert between a lipid-free and a lipid-bound form in a facile manner, a remarkable property conferred by the helix bundle motif. Composed of a series of four or five amphipathic alpha-helices that fold to form a helix bundle, this motif allows the en face orientation of the hydrophobic faces of the alpha-helices in the protein interior in the lipid-free state. A conformational switch then permits helix-helix interactions to be substituted by helix-lipid interactions upon lipid binding interaction. This review compares the apolipoprotein high-resolution structures and the factors that trigger this switch in insect apolipophorin III and the mammalian apolipoproteins, apolipoprotein E and apolipoprotein A-I, pointing out the commonalities and key differences in the mode of lipid interaction. Further insights into the lipid-bound conformation of apolipoproteins are required to fully understand their functional role under physiological conditions.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Apolipoproteins / chemistry*
  • Apolipoproteins / metabolism
  • Humans
  • Lipid Metabolism
  • Lipids / chemistry*
  • Models, Molecular
  • Protein Binding
  • Protein Conformation
  • Protein Folding*
  • Protein Structure, Secondary*


  • Apolipoproteins
  • Lipids