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NMR Studies of Human Apolipoprotein-AI


EMSL Project ID
2428

Abstract

In this proposal, we plan to focus on determining the NMR structure of lipid-free human apoA-I(1-186). ApoA-I is a 243-residue protein (28.1 kDa), which is the main protein component of HDL, a lipoprotein particle with good cholesterol. A higher level of HDL is well-correlated with a lower risk of heart diseases. ApoAI also serves as a ligand of the HDL receptor, SR-BI, and an activator of LCAT, a key enzyme in reverse cholesterol transport. Unfortunately, there are not many structural studies reported to date for this important plasma protein. In 1997, a X-ray crystal structure of apoA-I(44-243) had been reported, however, this structure was not able to explain the structure/functional data of apoA-I. One difficulty for structural study of apoA-I is that this protein aggregates at a very low concentration. The aggregation property prevents apoAI from crystallization. Therefore, we propose to determine the structure of apoA-I using NMR techniques. Our preliminary data indicated that full-length apoA-I aggregates under NMR sample concentration (~ 1 mM), however, apoA-I(1-186) aggregates much less than full-length apoA-I (data not shown). We have worked out an NMR experimental condition in which apoA-I(1-186) is monomeric at ~1 mM concentration. Thus, we are in a good position to carry out a complete structural study of this apoAI truncation mutant using NMR techniques. We believe that this study serves as a first step towards NMR studies of full-length apoA-I. This proposal is supported by a grant from the International HDL Research Award. We anticipate that the structures of human apoA-I will help us understand how apoA-I recruits lipids to initiate HDL formation and how apoA-I promotes HDL to recruit more neutral lipids, two central roles played by apoA-I in reverse cholesterol transport. Since a low level of plasma HDL and a compromised HDL function are the common thread of metabolic disorders/diseases including: atherosclerosis, diabetes, obesity, stroke, and Alzheimer's diseases, the results obtained from this proposal should have significant implications for the intervention of new medicine to treat these metabolic disorders/diseases.

Project Details

Project type
Capability Research
Start Date
2002-04-17
End Date
2002-08-30
Status
Closed

Team

Principal Investigator

Jianjun Wang
Institution
Wayne State University

Team Members

Arun Sivashanmugam
Institution
Wayne State University

Related Publications

Apolipoprotein AI tertiary structures determine stability and phospholipidbinding activity of discoidal high-density lipoprotein particles of different sizes Bin Chen, Xuefeng Ren, Tracey Neville, Gray Jerome, David W. Hoyt, Daniel Sparks, Gang Ren, and Jianjun Wang Received 14 November 2008; Revised 25 February 2009; Accepted 26 February 2009 DOI: 10.1002/pro.101 Published online 16 March 2009 proteinscience.org