Truncation of the amino terminus of human apolipoprotein A-I substantially alters only the lipid-free conformation.

Academic Article

Abstract

  • An amino-terminal deletion mutant (residues 1-43) of human apolipoprotein A-I (apo hA-I) has been produced from a bacterial expression system to explore the structural and functional role of these amino acids, encoded by exon 3, in apo hA-I. Lipid binding of apo delta (1-43)A-I and lipid binding of apo hA-I are very similar as assessed by surface activity, lipid association with palmitoyloleoylphosphatidylcholine (POPC) vesicles, and lipid association with plasma lipoproteins. Preliminary kinetic measurements appear to show that the reactivity of lecithin:cholesterol acyltransferase (LCAT) with the mutant is slightly decreased compared to wild-type apo hA-I. Collectively, these results indicate that the N-terminal region is not necessary for lipid binding or activation of LCAT. In contrast, there are significant structural differences between lipid-free apo delta (1-43)A-I and apo hA-I, as judged by denaturant-induced unfolding, binding of the fluorescent probe 1-anilinonaphthalene-8-sulfonate, surface balance measurements, and far- and near-ultraviolet circular dichroic spectroscopy. All spectral and physical measurements indicate apo delta (1-43)A-I has a folded, tertiary structure, although it is significantly less stable than that of apo hA-I. It is concluded that the N-terminal 43 residues are an important structural element of the lipid-free conformational state of apo hA-I, the absence of which induces a fundamentally different fold for the remaining carboxy-terminal residues, compared to those in native apo hA-I.
  • Published In

  • Biochemistry  Journal
  • Keywords

  • Anilino Naphthalenesulfonates, Apolipoprotein A-I, Binding Sites, Calorimetry, Circular Dichroism, Cloning, Molecular, DNA Primers, Escherichia coli, Fluorescent Dyes, Humans, Kinetics, Phosphatidylcholine-Sterol O-Acyltransferase, Phosphatidylcholines, Polymerase Chain Reaction, Protein Conformation, Protein Denaturation, Protein Folding, Recombinant Proteins, Sequence Deletion, Spectrometry, Fluorescence, Spectrophotometry, Ultraviolet, Substrate Specificity, Thermodynamics
  • Digital Object Identifier (doi)

    Authorlist

  • Rogers DP; Brouillette CG; Engler JA; Tendian SW; Roberts L; Mishra VK; Anantharamaiah GM; Lund-Katz S; Phillips MC; Ray MJ
  • Start Page

  • 288
  • End Page

  • 300
  • Volume

  • 36
  • Issue

  • 2