Structural Determination of Apolipoprotein/HDL Particles
EMSL Project ID
3367
Abstract
This research proposal is focused on determining the NMR structure of an exchangeable apolipoprotein,apolipophorin-III, that is associated with high-density lipoprotein (HDL). This is an important, unsolved
biological question since HDL particles play critical roles in clearance of excess cholesterol in peripheral
tissue, thus preventing atherosclerosis. Thus, this project is directly related to human diseases. We have
solved the NMR structures of two lipid-free full-length apoLp-IIIs, M. sexta apoLp-III (166-residues, Wang et
al, 1997, 2002) and L. migratoria apoLp-III (164-residues, Fan et al, 2001, Fan et al, 2003). Our hypothesis is
that upon lipid-binding, the lipid-free apoLp-III helix-bundle opens at hinges at one end of the molecule,
adopting an extended α-helical structure that exposes hydrophobic surfaces for lipid-binding. Previous
experimental evidence strongly supports this hypothesis. However, a final confirmation of this hypothesis
requires a lipid-bound structure of apoLp-III and currently we do NOT have such a structure available. A
structural study of apoLp-III/HDL using x-ray crystallography is impossible, since it resists crystallization. We
have collected significant preliminary data for this project, allowing us to demonstrate the feasibility of this
difficult project. Our immediate goal is to develop this project for NIH/NSF funding. However, we feel that we
will have better position for NIH funding if we can collect more preliminary data that we propose to collect at
PNNL. In our last proposal, we planed to carry out TROSY-type NMR experiments for apoLp-III/rHDL
particles. However, our sample went bad during these experiments, thus we did not collect useful data at that
time. Since the lipid-bound apoLp-III gives particle sizes of 43.3 kDa (for apoLp-III/DPC), 61.1 kDa (for
apoLp-III/Preβ-HDL) and ~180 kDa (for apoEC/rHDL), a high-field NMR instrument is very critical for this
project and we do not have such an instrument in our institution.
Project Details
Project type
Capability Research
Start Date
2003-04-12
End Date
2004-04-09
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Chen B, X Ren, T Neville, WG Jerome, DW Hoyt, DL Sparks, G Ren, and J Wang. 2009. "Apolipoprotein AI tertiary structures determine stability and phospholipid-binding activity of discoidal high-density lipoprotein particles of different sizes." Protein Science 18(5):921-935. doi:10.1002/pro.101