1B68

APOLIPOPROTEIN E4 (APOE4), 22K FRAGMENT

PDB DOI: 10.2210/pdb1B68/pdb

Classification: LIPID TRANSPORT
Organism(s): Homo sapiens
Expression System: Escherichia coli BL21
Mutation(s): No

Deposited: 1999-01-21 Released: 2001-07-11
Deposition Author(s): Rupp, B., Peters-Libeu, C.

Experimental Data Snapshot

Method: X-RAY DIFFRACTION
Resolution: 2.00 Å
R-Value Free: 0.255
R-Value Work: 0.200
R-Value Observed: 0.200

wwPDB Validation 3D Report Full Report

This is version 1.2 of the entry. See complete history.

Literature

Interaction of the N-terminal domain of apolipoprotein E4 with heparin.

Dong, J., Peters-Libeu, C.A., Weisgraber, K.H., Segelke, B.W., Rupp, B., Capila, I., Hernaiz, M.J., LeBrun, L.A., Linhardt, R.J.

(2001) Biochemistry 40: 2826-2834

PubMed: 11258893 Search on PubMed
DOI: 10.1021/bi002417n
Primary Citation of Related Structures:
1B68

PubMed Abstract:

Apolipoprotein E (apoE) is an important lipid-transport protein in human plasma and brain. It has three common isoforms (apoE2, apoE3, and apoE4). ApoE is a major genetic risk factor in heart disease and in neurodegenerative disease, including Alzheimer's disease. The interaction of apoE with heparan sulfate proteoglycans plays an important role in lipoprotein remnant uptake and likely in atherogenesis and Alzheimer's disease. Here we report our studies of the interaction of the N-terminal domain of apoE4 (residues 1-191), which contains the major heparin-binding site, with an enzymatically prepared heparin oligosaccharide. Identified by its high affinity for the N-terminal domain of apoE4, this oligosaccharide was determined to be an octasaccharide of the structure DeltaUAp2S(1-->[4)-alpha-D-GlcNpS6S(1-->4)-alpha-L-IdoAp2S(1-->](3)4)-alpha-D-GlcNpS6S by nuclear magnetic resonance spectroscopy, capillary electrophoresis, and polyacrylamide gel electrophoresis. Kinetic analysis of the interaction between the N-terminal apoE4 fragment and immobilized heparin by surface plasmon resonance yielded a K(d) of 150 nM. A similar binding constant (K(d) = 140 nM) was observed for the interaction between immobilized N-terminal apoE4 and the octasaccharide. Isothermal titration calorimetry revealed a K(d) of 75 nM for the interaction of the N-terminal apoE fragment and the octasaccharide with a binding stoichiometry of approximately 1:1. Using previous studies and molecular modeling, we propose a binding site for this octasaccharide in a basic residue-rich region of helix 4 of the N-terminal fragment. From the X-ray crystal structure of the N-terminal apoE4, we predicted that binding of the octasaccharide at this site would result in a change in intrinsic fluorescence. This prediction was confirmed experimentally by an observed increase in fluorescence intensity with octasaccharide binding corresponding to a K(d) of approximately 1 microM.

Organizational Affiliation:

Gladstone Institute of Cardiovascular Disease, Cardiovascular Research Institute, and Department of Pathology, University of California, San Francisco, California 94941-9100, USA.

Macromolecules

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(by identity cutoff) | 3D Structure

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
APOLIPOPROTEIN E	A	191	Homo sapiens	Mutation(s): 0 Gene Names: APOE
UniProt & NIH Common Fund Data Resources
Find proteins for P02649 (Homo sapiens) Explore P02649 Go to UniProtKB: P02649
PHAROS: P02649 GTEx: ENSG00000130203
Entity Groups
Sequence Clusters	30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt Group	P02649
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Reference Sequence