Electron paramagnetic resonance spectroscopy of site-directed spin labels reveals the structural heterogeneity in the N-terminal domain of apoA-I in solution

Research output: Contribution to journalArticle


Apolipoprotein A-I (apoA-I) is the major protein constituent of high density lipoprotein (HDL) and plays a central role in phospholipid and cholesterol metabolism. This 243-residue long protein is remarkably flexible and assumes numerous lipid-dependent conformations. Consequently, definitive structural determination of lipid-free apoA-I in solution has been difficult. Using electron paramagnetic spectroscopy of site-directed spin labels in the N-terminal domain of apoA-I (residues 1-98) we have mapped a mixture of secondary structural elements, the composition of which is consistent with findings from other in-solution methods. Based on side chain mobility and their accessibility to polar and non-polar spin relaxers, the precise location of secondary elements for amino acids 14-98 was determined for both lipid-free and lipid-bound apoA-I. Based on intermolecular dipolar coupling at positions 26, 44, and 64, these secondary structural elements were arranged into a tertiary fold to generate a structural model for lipid-free apoA-I in solution.


External organisations
  • University of California System
Research areas and keywords


  • Apolipoprotein A-I, Crystallization, Dimerization, Electron Spin Resonance Spectroscopy, Humans, Lipids, Models, Molecular, Molecular Conformation, Mutagenesis, Protein Binding, Protein Conformation, Protein Folding, Protein Structure, Secondary, Protein Structure, Tertiary, Spin Labels, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't
Original languageEnglish
Pages (from-to)9143-9
JournalJournal of Biological Chemistry
Issue number12
Publication statusPublished - 2007 Mar 23
Publication categoryResearch
Externally publishedYes