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Structural Studies of Lipid-free Apolipoprotein A-I

EMSL Project ID


Apolipoprotein A-I (apoAI) is a 243-residue exchangeable apolipoprotein that plays a key role in clearing the "bad cholesterol" from the human blood stream (reverse cholesterol transport. ApoAI is the most abundant protein component in high-density lipoprotein (HDL, ~70%). Depending on the extent of lipidation, apoAI displays a dramatic conformational plasticity and may adopt one of four distinct conformations, including: (1). Lipid-free apoAI conformation (for specific phospholipid-binding, M.W.: 28 kDa). (2). ApoAI on preb-HDL (for specific cholesterol-binding, M.W.: ~55 kDa). (3). ApoAI on discoidal HDL (for specific LCAT activation, M.W.: ~140-160 kDa). (4). ApoAI on spherical HDL (for specific HDL-receptor binding, M.W.: 12-180 kDa). We plan to solve lipid-free apoAI conformation. In order to achieve this goal, we prepared a monomeric mouse apoAI(1-216), solved aggregation problem in structural studies of apoAI. ApoAI(1-216) contains most of the regions that are responsible for its activity, and the C-terminal 24-residues are unstructured in the lipid-free state, the NMR structure of apoAI(1-216) should represent the structure of lipid-free apoAI. In this proposal, we request a 600MHz (with a cold probe) time for one week, and a 800MHz time for one week. The 600MHz NMR time is for the measurement of 3D CCC-TOCSY-NNH and HCC-TOCSY-NNH. The 800 MHz NMR time is for 3D 15N-edited NOESY with both perdeuterated and 30% deuterated triple-labeled apoAI(1-216) samples. We are currently collecting 3D triple-resonance NMR spectra. With these NMR data, we will be able to carry out a complete NMR spectral assignment of this protein, which is the first step towards the structural determination of lipid-free apoAI.

Project Details

Project type
Capability Research
Start Date
End Date


Principal Investigator

Jianjun Wang
Wayne State University

Team Members

Arun Sivashanmugam
Wayne State University

Bin Chen
Wayne State University

Related Publications

A complete NMR spectral assignment of the lipid-free mouse apolipoprotein A-I (apoAI) C-terminal truncation mutant, apoAI(1-216) Biomol NMR Assign (2007) 1:109–111 DOI 10.1007/s12104-007-9031-2
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