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PLoS One. 2011 May 9;6(5):e18841. doi: 10.1371/journal.pone.0018841.

Three-dimensional cryoEM reconstruction of native LDL particles to 16Å resolution at physiological body temperature.

Author information

  • 1Department of Biomedical Engineering and Computational Science, School of Science and Technology, Centre of Excellence in Computational Complex Systems Research, Aalto University Aalto, Finland.

Abstract

BACKGROUND:

Low-density lipoprotein (LDL) particles, the major carriers of cholesterol in the human circulation, have a key role in cholesterol physiology and in the development of atherosclerosis. The most prominent structural components in LDL are the core-forming cholesteryl esters (CE) and the particle-encircling single copy of a huge, non-exchangeable protein, the apolipoprotein B-100 (apoB-100). The shape of native LDL particles and the conformation of native apoB-100 on the particles remain incompletely characterized at the physiological human body temperature (37 °C).

METHODOLOGY/PRINCIPAL FINDINGS:

To study native LDL particles, we applied cryo-electron microscopy to calculate 3D reconstructions of LDL particles in their hydrated state. Images of the particles vitrified at 6 °C and 37 °C resulted in reconstructions at ~16 Å resolution at both temperatures. 3D variance map analysis revealed rigid and flexible domains of lipids and apoB-100 at both temperatures. The reconstructions showed less variability at 6 °C than at 37 °C, which reflected increased order of the core CE molecules, rather than decreased mobility of the apoB-100. Compact molecular packing of the core and order in a lipid-binding domain of apoB-100 were observed at 6 °C, but not at 37 °C. At 37 °C we were able to highlight features in the LDL particles that are not clearly separable in 3D maps at 6 °C. Segmentation of apoB-100 density, fitting of lipovitellin X-ray structure, and antibody mapping, jointly revealed the approximate locations of the individual domains of apoB-100 on the surface of native LDL particles.

CONCLUSIONS/SIGNIFICANCE:

Our study provides molecular background for further understanding of the link between structure and function of native LDL particles at physiological body temperature.

PMID:
21573056
[PubMed - indexed for MEDLINE]
PMCID:
PMC3090388
Free PMC Article

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