Structure of apolipoprotein A-I N terminus on nascent high density lipoproteins

Jens O. Lagerstedt, Giorgio Cavigiolio, Madhu S. Budamagunta, Ioanna Pagani, John C Voss, Michael N. Oda

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Abstract

Apolipoprotein A-I (apoA-I) is the major protein component of high density lipoproteins (HDL) and a critical element of cholesterol metabolism. To better elucidate the role of the apoA-I structure-function in cholesterol metabolism, the conformation of the apoA-I N terminus (residues 6-98) on nascent HDL was examined by electron paramagnetic resonance (EPR) spectroscopic analysis. A series of 93 apoA-I variants bearing single nitroxide spin label at positions 6-98 was reconstituted onto 9.6-nm HDL particles (rHDL). These particles were subjected to EPR spectral analysis, measuring regional flexibility and side chain solvent accessibility. Secondary structure was elucidated from side-chain mobility and molecular accessibility, wherein two major α-helical domains were localized to residues 6-34 and 50-98. We identified an unstructured segment (residues 35-39) and a α-strand (residues 40-49) between the two helices. Residues 14, 19, 34, 37, 41, and 58 were examined by EPR on 7.8, 8.4, and 9.6 nm rHDL to assess the effect of particle size on the N-terminal structure. Residues 14, 19, and 58 showed no significant rHDL size-dependent spectral or accessibility differences, whereas residues 34, 37, and 41 displayed moderate spectral changes along with substantial rHDL size-dependent differences in molecular accessibility. We have elucidated the secondary structure of the N-terminal domain of apoA-I on 9.6 nm rHDL (residues 6-98) and identified residues in this region that are affected by particle size. We conclude that the inter-helical segment (residues 35-49) plays a role in the adaptation of apoA-I to the particle size of HDL.

Original languageEnglish (US)
Pages (from-to)2966-2975
Number of pages10
JournalJournal of Biological Chemistry
Volume286
Issue number4
DOIs
StatePublished - Jan 28 2011

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

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    Lagerstedt, J. O., Cavigiolio, G., Budamagunta, M. S., Pagani, I., Voss, J. C., & Oda, M. N. (2011). Structure of apolipoprotein A-I N terminus on nascent high density lipoproteins. Journal of Biological Chemistry, 286(4), 2966-2975. https://doi.org/10.1074/jbc.M110.163097