ジャーナル: PLoS One / 年: 2011 タイトル: Three-dimensional cryoEM reconstruction of native LDL particles to 16Å resolution at physiological body temperature. 著者: Vibhor Kumar / Sarah J Butcher / Katariina Öörni / Peter Engelhardt / Jukka Heikkonen / Kimmo Kaski / Mika Ala-Korpela / Petri T Kovanen / 要旨: 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. ...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 ...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.
名称: LDL at 37C / タイプ: sample / ID: 1000 詳細: Samples were vitrified on Quantifoil holey carbon grids (Quantifoil Micro Tools, GmbH) either at 6C or 37C, allowing pre-equilibration of the sample at the desired temperature for at least 45 ...詳細: Samples were vitrified on Quantifoil holey carbon grids (Quantifoil Micro Tools, GmbH) either at 6C or 37C, allowing pre-equilibration of the sample at the desired temperature for at least 45 minutes prior to plunging. Number unique components: 1
Initially only phase-flipping was carried out to correct for the contrast transfer function. To reduce the effect of image noise and artefacts, an initial single particle reconstruction was made on images de-noised with an information theory [Minimum Description Length (MDL)] based method which we have introduced earlier. Fifty initial class averages were obtained using a reference-free classification of 3000 images by multivariate statistical analysis using parameters, as suggested in EMAN . Angles were assigned using the cross common lines method prior to reconstruction using weighted-back projection. The initial 3D models were low-pass filtered. The 2D image dataset was increased to include all of the particles and iterative refinement continued. After each iteration of the single-particle-reconstruction process only 75% of the images with the highest correlation values were chosen. In order to avoid any bias in 3D reconstruction due to the de-noising, the final reconstructions were made using raw images after being assigned to classes using their de-noised equivalents
CTF補正
詳細: Each particle
最終 再構成
想定した対称性 - 点群: C1 (非対称) / アルゴリズム: OTHER / 解像度のタイプ: BY AUTHOR / 解像度: 16.0 Å / 解像度の算出法: FSC 0.5 CUT-OFF / ソフトウェア - 名称: EMAN / 使用した粒子像数: 29844