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 language | English (US) |
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Pages (from-to) | 190-197 |
Number of pages | 8 |
Journal | Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism |
Volume | 488 |
Issue number | 2 |
DOIs | |
State | Published - Aug 24 1977 |
ASJC Scopus subject areas
- Biophysics
- Biochemistry
- Endocrinology