Properties of the retained N-terminal hydrophobic leader sequence in human serum paraoxonase/arylesterase

Chem Biol Interact. 1999 May 14;119-120:243-9. doi: 10.1016/s0009-2797(99)00033-2.

Abstract

Human serum paraoxonase/arylesterase (PON1) is HDL-associated and appears to protect low density lipoproteins (LDL) from oxidation. Mature PON1 retains its N-terminal hydrophobic signal sequence, which may be needed for binding to HDL. By site-directed mutagenesis, we created a mutant PON1 (A19A20) with a cleavable N-terminus to determine if this peptide mediated binding to lipoproteins. As a model system, we studied binding of mutant and wild type PON1s to lipoproteins in fetal bovine serum-containing expression medium and found that the wild type recombinant enzyme associated with lipoproteins whereas the A19A20 mutant did not. These results show that the N-terminus is required for binding to either apolipoproteins or phospholipids. Furthermore, we showed that wild type enzyme can bind to phospholipids directly without apolipoproteins. To determine if lipid binding is a requirement for PON1's protection against LDL oxidation, we used a copper ion-induced oxidation system and found that the wild type enzyme and A19A20 mutant showed similar reductions in both peroxide and aldehyde formation. We conclude that PON1 depends upon its N-terminal hydrophobic peptide for its association with serum lipoproteins.

MeSH terms

  • Animals
  • Apolipoprotein A-I / chemistry
  • Aryldialkylphosphatase
  • Carboxylic Ester Hydrolases / blood*
  • Carboxylic Ester Hydrolases / chemistry
  • Carboxylic Ester Hydrolases / genetics
  • Cattle
  • Chickens
  • Cholesterol / chemistry
  • Copper / pharmacology
  • Esterases / blood*
  • Esterases / chemistry
  • Esterases / genetics
  • Humans
  • Kinetics
  • Lipoproteins / chemistry
  • Lipoproteins, LDL / chemistry
  • Mutagenesis, Site-Directed
  • Oxidative Stress
  • Peptide Fragments / blood
  • Peptide Fragments / chemistry
  • Peptide Fragments / genetics
  • Phospholipids / chemistry
  • Protein Binding / genetics
  • Protein Sorting Signals / blood*
  • Protein Sorting Signals / chemistry
  • Protein Sorting Signals / genetics

Substances

  • Apolipoprotein A-I
  • Lipoproteins
  • Lipoproteins, LDL
  • Peptide Fragments
  • Phospholipids
  • Protein Sorting Signals
  • Copper
  • Cholesterol
  • Esterases
  • Carboxylic Ester Hydrolases
  • arylesterase
  • Aryldialkylphosphatase
  • PON1 protein, human