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NMR Studies of Human Apolipoprotein-E N-terminal Domain


EMSL Project ID
2299

Abstract

This research proposal is centered on NMR structural studies of human apolipoprotein-E (apoE). ApoE plays important roles in several human diseases, including atherosclerosis and Alzheimer’s diseases. We will particularly focus on solving the full-length apoE N-terminal domain, apoE(1-183). Although there is a X-ray crystal structure available for this domain, this structure only contains residue 23-166, whereas the rest of the regions have not yet been seen in the crystal structure (Wilson et al, 1991). Recent experimental data indicates that several residues beyond region 23-166 are critical in apoE LDL receptor binding activity (Weisgraber, 1991, 1994, Morrow et al, 2000). For example, mutation of residue 172 displays only 2% LDL receptor binding activity of apoE (Morrow, et al. 2000). Further, the truncation mutants 1-166 and 1-170 show only 1% LDL receptor binding activity, whereas the 1-174 variant possessed 17% normal binding activity (Weisgraber 1994). These results indicate that more structural studies of the apoE N-terminal domain are required to resolve these problems. The X-ray crystal structure indicates that residues beyond 23-164, either at the N-terminus or the C-terminus, are flexible and have no observable electron density map in the X-ray diffraction. Thus, NMR structural studies of the apoE N-terminal domain may provides a possible solution to these issues. Further, preliminary experimental evidence suggests that apoE(1-183) provides the complete LDL receptor binding activity for apoE (Weisgraber, 1994). We have 2H/15N/13C-triple labeled apoE(1-183) for 3D/4D heteronuclear NMR experiments. Our preliminary NMR studies indicated that apoE(1-183) adopted a similar helix-bundle structure at several different pHs, including pH6.4 and 3.2. Our NMR data further indicates the presence of NMR signals for those residues beyond 23-164 region, suggesting the possibility of a complete NMR assignment for intact apoE(1-183). In addition, this result also suggests that we may obtain a NMR structure of an intact apoE N-terminal domain in solution. We anticipate that a NMR structure of the intact apoE N-terminal domain may provide answers to the above important issues pertaining to the apoE LDL receptor binding activity.

Project Details

Project type
Capability Research
Start Date
2001-10-23
End Date
2002-08-30
Status
Closed

Team

Principal Investigator

Jianjun Wang
Institution
Wayne State University

Team Members

Xuefeng Ren
Institution
Wayne State University

So-Young Shin
Institution
Wayne State University

Jianglei Chen
Institution
Wayne State University

Bin Chen
Institution
Wayne State University

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