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Thermodynamic analysis of human plasma apolipoprotein C-1: high-temperature unfolding and low-temperature oligomer dissociation.
Biochemistry. 1998 Feb 03; 37(5):1283-91.B

Abstract

Thermal and chemical unfolding of lipid-free apolipoprotein C-1 (apoC-1), a 6-kDa protein component of very low density and high-density lipoproteins, was analyzed by far-UV CD. In neutral 1 mM Na2HPO4 solutions containing 6-7 micrograms/mL protein, the apoC-1 monomer is approximately 30% alpha-helical at 0-22 degrees C and unfolds reversibly from about 22-80 degrees C with Tm = 51 +/- 3 degrees C and van't Hoff enthalpy delta Hv(Tm) = 19 +/- 3 kcal/mol. The apparent free energy of the monomer stabilization determined from the chemical unfolding at 0 degree C, delta G(0 degree C) = 2.8 +/- 0.8 kcal/mol, decreases by about 1 kcal/mol upon heating to 25 degrees C. A small apparent heat capacity increment suggests the absence of a substantial hydrophobic core for the apoC-1 molecule. At pH 7, increasing apoC-1 concentration above 10 micrograms/mL leads to self-association and formation of additional alpha-helices that unfold upon both heating and cooling from room temperature. The CD data indicate that the high-temperature transition reflects a complete monomer unfolding and the low-temperature transition reflects oligomer dissociation into stable monomers. This suggests the importance of hydrophobic interactions for apoC-1 self-association. Close proximity between the high- and low-temperature transitions and the absence of a plateau in the chemical unfolding curves recorded from oligomeric apoC-1 indicate marginal oligomer stability and suggest that in vivo apoC-1 transfer is mediated via the complexes with other apolipoproteins and/or lipids.

Authors+Show Affiliations

Gursky O
Department of Biophysics, Boston University School of Medicine, Massachusetts 02118, USA. gursky@med-biophd.bu.edu
Atkinson D
No affiliation info available

MeSH

AcetatesApolipoprotein C-IApolipoproteins CBuffersCircular DichroismCold TemperatureGuanidineHot TemperatureHumansHydrogen-Ion ConcentrationPhosphatesProtein DenaturationProtein FoldingProtein Structure, SecondaryThermodynamics

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9477954

Citation

Gursky, O, and D Atkinson. "Thermodynamic Analysis of Human Plasma Apolipoprotein C-1: High-temperature Unfolding and Low-temperature Oligomer Dissociation." Biochemistry, vol. 37, no. 5, 1998, pp. 1283-91.
Gursky O, Atkinson D. Thermodynamic analysis of human plasma apolipoprotein C-1: high-temperature unfolding and low-temperature oligomer dissociation. Biochemistry. 1998;37(5):1283-91.
Gursky, O., & Atkinson, D. (1998). Thermodynamic analysis of human plasma apolipoprotein C-1: high-temperature unfolding and low-temperature oligomer dissociation. Biochemistry, 37(5), 1283-91.
Gursky O, Atkinson D. Thermodynamic Analysis of Human Plasma Apolipoprotein C-1: High-temperature Unfolding and Low-temperature Oligomer Dissociation. Biochemistry. 1998 Feb 3;37(5):1283-91. PubMed PMID: 9477954.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Thermodynamic analysis of human plasma apolipoprotein C-1: high-temperature unfolding and low-temperature oligomer dissociation. AU - Gursky,O, AU - Atkinson,D, PY - 1998/3/7/pubmed PY - 1998/3/7/medline PY - 1998/3/7/entrez SP - 1283 EP - 91 JF - Biochemistry JO - Biochemistry VL - 37 IS - 5 N2 - Thermal and chemical unfolding of lipid-free apolipoprotein C-1 (apoC-1), a 6-kDa protein component of very low density and high-density lipoproteins, was analyzed by far-UV CD. In neutral 1 mM Na2HPO4 solutions containing 6-7 micrograms/mL protein, the apoC-1 monomer is approximately 30% alpha-helical at 0-22 degrees C and unfolds reversibly from about 22-80 degrees C with Tm = 51 +/- 3 degrees C and van't Hoff enthalpy delta Hv(Tm) = 19 +/- 3 kcal/mol. The apparent free energy of the monomer stabilization determined from the chemical unfolding at 0 degree C, delta G(0 degree C) = 2.8 +/- 0.8 kcal/mol, decreases by about 1 kcal/mol upon heating to 25 degrees C. A small apparent heat capacity increment suggests the absence of a substantial hydrophobic core for the apoC-1 molecule. At pH 7, increasing apoC-1 concentration above 10 micrograms/mL leads to self-association and formation of additional alpha-helices that unfold upon both heating and cooling from room temperature. The CD data indicate that the high-temperature transition reflects a complete monomer unfolding and the low-temperature transition reflects oligomer dissociation into stable monomers. This suggests the importance of hydrophobic interactions for apoC-1 self-association. Close proximity between the high- and low-temperature transitions and the absence of a plateau in the chemical unfolding curves recorded from oligomeric apoC-1 indicate marginal oligomer stability and suggest that in vivo apoC-1 transfer is mediated via the complexes with other apolipoproteins and/or lipids. SN - 0006-2960 UR - https://www.unboundmedicine.com/medline/citation/9477954/Thermodynamic_analysis_of_human_plasma_apolipoprotein_C_1:_high_temperature_unfolding_and_low_temperature_oligomer_dissociation_ L2 - https://doi.org/10.1021/bi971801q DB - PRIME DP - Unbound Medicine ER -