Biotechnology and Biological Sciences Research Council (BBSRC)
95519980
英国
引用
ジャーナル: J Struct Biol / 年: 2025 タイトル: Untangling the effects of flexibility and the AWI in cryoEM sample preparation: A case study using KtrA. 著者: Isobel Jackson Hirst / Wesley Tien Chiang / Nien-Jen Hu / Charlotte A Scarff / Rebecca F Thompson / Michele C Darrow / Stephen P Muench / 要旨: Single particle cryo-electron microscopy (cryoEM) is a powerful tool for elucidating the structures of biological macromolecules without requiring crystallisation or fixation. However, certain ...Single particle cryo-electron microscopy (cryoEM) is a powerful tool for elucidating the structures of biological macromolecules without requiring crystallisation or fixation. However, certain barriers to obtaining high-resolution structures persist, particularly during grid preparation when samples are in a thin liquid film. At this stage, extensive exposure to the air-water interface (AWI) can lead to subunit dissociation, denaturation, and preferred orientation of particles. Another obstacle to high-resolution cryoEM is molecular flexibility, which introduces heterogeneity in the dataset, weakening the signal during image processing. This study explores the effects of AWI interactions and molecular flexibility on the cryoEM density maps of KtrA, the soluble regulatory subunit of the potassium transporter KtrAB from Bacillus subtilis. From grids prepared using a standard blotting technique, we observed a lack of density in the C-lobe domains and preferred orientation. Modifications such as reducing AWI exposure through faster vitrification times (6 s vs ≤100 ms) notably improved C-lobe density. Moreover, the addition of cyclic di-AMP, which binds to the C-lobes, combined with a 100 ms plunge time, further enhanced C-lobe density and eliminated preferred orientation. These findings demonstrate that both AWI interactions and flexibility had to be addressed to obtain density for the C-lobe domains of KtrA. This study underscores the ongoing complexities in achieving high-resolution cryoEM for many samples.
This is the map after it has been low pass filtered in EMAN to 8 A. This map was used for comparison and is the one that is showed in figure 3 in the corresponding paper.
全体 : KtrA, the regulatory subunit from the KtrAB potassium transporter
全体
名称: KtrA, the regulatory subunit from the KtrAB potassium transporter
要素
複合体: KtrA, the regulatory subunit from the KtrAB potassium transporter
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超分子 #1: KtrA, the regulatory subunit from the KtrAB potassium transporter
超分子
名称: KtrA, the regulatory subunit from the KtrAB potassium transporter タイプ: complex / ID: 1 / 親要素: 0 詳細: This is map is part of an investigation into the effects of sample preparation on map quality.
由来(天然)
生物種: Bascillus subtilis (枯草菌)
分子量
理論値: 198 KDa
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実験情報
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構造解析
手法
クライオ電子顕微鏡法
解析
単粒子再構成法
試料の集合状態
particle
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試料調製
濃度
8 mg/mL
緩衝液
pH: 8 構成要素:
濃度
式
名称
150.0 mM
KCl
potassium chloride
50.0 mM
Tris
詳細: 50 mM Tris-HCl, 150 mM KCl, 0.5 mM TCEP 0.00087% DDM added just before grids were made
凍結
凍結剤: ETHANE / チャンバー内湿度: 100 % / チャンバー内温度: 277 K / 装置: SPOTITON 詳細: The commercialised version of the spotiton, the chameleon was used with a plunge time of 180 ms. In-house self wicking grids from SPT Labtech were used..
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電子顕微鏡法
顕微鏡
TFS KRIOS
撮影
フィルム・検出器のモデル: FEI FALCON IV (4k x 4k) 撮影したグリッド数: 1 / 実像数: 4278 / 平均露光時間: 4.0 sec. / 平均電子線量: 43.0 e/Å2