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The helix bundle: A reversible lipid binding motif

Authors
Journal
Comparative Biochemistry and Physiology Part A Molecular & Integrative Physiology
1095-6433
Publisher
Elsevier
Publication Date
Volume
155
Issue
2
Identifiers
DOI: 10.1016/j.cbpa.2009.09.009
Keywords
  • Apolipophorin
  • Apolipoprotein
  • Lipophorin
  • Lipoprotein
  • Protein Structure
  • Cholesterol
  • Diacylglycerol
  • Triacylglycerol
Disciplines
  • Biology

Abstract

Abstract 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 α-helices that fold to form a helix bundle, this motif allows the en face orientation of the hydrophobic faces of the α-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.

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