ジャーナル: Sci Rep / 年: 2024 タイトル: Use of phase plate cryo-EM reveals conformation diversity of therapeutic IgG with 50 kDa Fab fragment resolved below 6 Å. 著者: Hsin-Hung Lin / Chun-Hsiung Wang / Shih-Hsin Huang / Sung-Yao Lin / Takayuki Kato / Keiichi Namba / Naoki Hosogi / Chihong Song / Kazuyoshi Murata / Ching-Hsuan Yen / Tsui-Ling Hsu / Chi-Huey ...著者: Hsin-Hung Lin / Chun-Hsiung Wang / Shih-Hsin Huang / Sung-Yao Lin / Takayuki Kato / Keiichi Namba / Naoki Hosogi / Chihong Song / Kazuyoshi Murata / Ching-Hsuan Yen / Tsui-Ling Hsu / Chi-Huey Wong / Yi-Min Wu / I-Ping Tu / Wei-Hau Chang / 要旨: While cryogenic electron microscopy (cryo-EM) is fruitfully used for harvesting high-resolution structures of sizable macromolecules, its application to small or flexible proteins composed of small ...While cryogenic electron microscopy (cryo-EM) is fruitfully used for harvesting high-resolution structures of sizable macromolecules, its application to small or flexible proteins composed of small domains like immunoglobulin (IgG) remain challenging. Here, we applied single particle cryo-EM to Rituximab, a therapeutic IgG mediating anti-tumor toxicity, to explore its solution conformations. We found Rituximab molecules exhibited aggregates in cryo-EM specimens contrary to its solution behavior, and utilized a non-ionic detergent to successfully disperse them as isolated particles amenable to single particle analysis. As the detergent adversely reduced the protein-to-solvent contrast, we employed phase plate contrast to mitigate the impaired protein visibility. Assisted by phase plate imaging, we obtained a canonical three-arm IgG structure with other structures displaying variable arm densities co-existing in solution, affirming high flexibility of arm-connecting linkers. Furthermore, we showed phase plate imaging enables reliable structure determination of Fab to sub-nanometer resolution from ab initio, yielding a characteristic two-lobe structure that could be unambiguously docked with crystal structure. Our findings revealed conformation diversity of IgG and demonstrated phase plate was viable for cryo-EM analysis of small proteins without symmetry. This work helps extend cryo-EM boundaries, providing a valuable imaging and structural analysis framework for macromolecules with similar challenging features.
名称: Fab domain of Rituximab / タイプ: complex / ID: 1 / 親要素: 0 詳細: The segmentation of Fab domain from Rituximab IgG was treated by using the PierceTM Fab preparation kit (Thermo Fisher Scientific Inc., Waltham, MA, USA)
由来(天然)
生物種: Mus musculus (ハツカネズミ)
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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
0.2 mg/mL
緩衝液
pH: 6.5
凍結
凍結剤: ETHANE / チャンバー内湿度: 98 % / チャンバー内温度: 277 K / 装置: FEI VITROBOT MARK IV
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電子顕微鏡法
顕微鏡
FEI TITAN KRIOS
撮影
フィルム・検出器のモデル: GATAN K3 (6k x 4k) / 検出モード: OTHER / 実像数: 50 / 平均電子線量: 1.01 e/Å2