Interfacial properties of a complex multi-domain 490 amino acid peptide derived from apolipoprotein B (residues 292-782)

Matthew A. Mitsche, Libo Wang, Z. Gordon Jiang, C. James McKnight, Donald M. Small

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


ApolipoproteinB (ApoB) is a lipid binding protein that is a nonexchangeable component of chylomicrons, VLDL, and LDL. In the liver and intestinal cells ApoB recruits lipid to form nascent triacylglycerol rich particles cotranslationally in the endoplasmic reticulum membrane which are then processed and secreted to form plasma lipoproteins. The N-terminal domain, which comprises the first 22% of apoB, recruits lipid in a controlled manner. The first 6% (residues 1 - 291) of the N-terminus does not bind lipid. The first lipid binding domain, including residues 292 - 782 (B6 - 17), forms a lipid binding pocket which is predicted to consist of 17 α-helices and 6 β-strands. A structural model based on the X-ray structure of the homologues protein lipovitellin suggests that the N-terminal 6 - 8 helices and the β-sheet interact with lipid while the C-terminal helices form a structural unit stabilizing the β-sheet. Using isothermal drop tensiometry we showed that ApoB6.4-17 is surface active and binds to a triolein/water interface and exerts 16-19 mN/m of pressure (II) on that surface. The protein initially adsorbs slowly from aqueous solution to the surface but following compression and re-expansion it reaches equilibrium much faster. When II exceeds 16.9 mN/m part of the protein is ejected from the surface, but when compressed to high II the protein is never completely ejected indicating that part of the peptide is irreversibly anchored to the interface. The surface dilation modulus (ε) varies between 25-38 mN/m, and is predominantly elastic with a small viscous component. When compressed at an air/water interface ApoB6.4-17 has a limiting area of ∼11 Å 2 per amino acid at lift off and only ∼7 Å 2 per amino acid at the collapse II (28 mN/m). These values are about half the anticipated values if all the residues are at the surface. This suggests that ApoB6.4-17 retains some globular structure at an interface and does not completely denature at the surface, as many other globular proteins do. We suggest that while bound to the surface ApoB6.4-17 exhibits properties of both α and β structure giving it unique and versatile characteristics at a hydrophobic interface.

Original languageEnglish (US)
Pages (from-to)2322-2330
Number of pages9
Issue number4
StatePublished - Feb 17 2009

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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