Thermodynamics of lipid protein associations thermodynamics of helix formation in the association of high density apolipoprotein A-I (ApoA-I) to dimyristoyl phosphatidylcholine

Henry J. Pownall, Fu Juan Hsu, Maryvonne Rosseneu, Hubert Peeters, Antonio Gotto, Richard L. Jackson

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

The structure and phospholipid-binding properties of human plasma high density apolipoprotein A-I (apoA-I) has been studied at pH 7.4 and 3.1 by microcalorimetry, circular dichroism and density gradient ultracentrifugation. At pH values of 7.4 and 3.1, apoA-I binds to dimyristoyl phosphatidylcholine (DMPC) to form complexes of similar composition (molar ratio of DMPC/ apoA-I of 100) and helical content (67%). At pH 7.4, the lipid-protein association is accompanied by an increase in helical content from 58 to 67% and an exothermic enthalpy of binding (ΔHB) of -90 kcal/mol apoA-I. At pH 3.1, the helical content of apoA-I is increased from 48 to 67% on binding to DMPC and the enthalpy of binding was -170 kcal/mol. We suggest that the difference in the enthalpies of binding (-80 kcal/mol) at pH 3.1 compared to 7.4 is due to the greater coil → helix transition at the lower pH.

Original languageEnglish (US)
Pages (from-to)190-197
Number of pages8
JournalBiochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism
Volume488
Issue number2
DOIs
StatePublished - Aug 24 1977

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Endocrinology

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