ジャーナル: Nature / 年: 2015 タイトル: Structure of the F-actin-tropomyosin complex. 著者: Julian von der Ecken / Mirco Müller / William Lehman / Dietmar J Manstein / Pawel A Penczek / Stefan Raunser / 要旨: Filamentous actin (F-actin) is the major protein of muscle thin filaments, and actin microfilaments are the main component of the eukaryotic cytoskeleton. Mutations in different actin isoforms lead ...Filamentous actin (F-actin) is the major protein of muscle thin filaments, and actin microfilaments are the main component of the eukaryotic cytoskeleton. Mutations in different actin isoforms lead to early-onset autosomal dominant non-syndromic hearing loss, familial thoracic aortic aneurysms and dissections, and multiple variations of myopathies. In striated muscle fibres, the binding of myosin motors to actin filaments is mainly regulated by tropomyosin and troponin. Tropomyosin also binds to F-actin in smooth muscle and in non-muscle cells and stabilizes and regulates the filaments there in the absence of troponin. Although crystal structures for monomeric actin (G-actin) are available, a high-resolution structure of F-actin is still missing, hampering our understanding of how disease-causing mutations affect the function of thin muscle filaments and microfilaments. Here we report the three-dimensional structure of F-actin at a resolution of 3.7 Å in complex with tropomyosin at a resolution of 6.5 Å, determined by electron cryomicroscopy. The structure reveals that the D-loop is ordered and acts as a central region for hydrophobic and electrostatic interactions that stabilize the F-actin filament. We clearly identify map density corresponding to ADP and Mg(2+) and explain the possible effect of prominent disease-causing mutants. A comparison of F-actin with G-actin reveals the conformational changes during filament formation and identifies the D-loop as their key mediator. We also confirm that negatively charged tropomyosin interacts with a positively charged groove on F-actin. Comparison of the position of tropomyosin in F-actin-tropomyosin with its position in our previously determined F-actin-tropomyosin-myosin structure reveals a myosin-induced transition of tropomyosin. Our results allow us to understand the role of individual mutations in the genesis of actin- and tropomyosin-related diseases and will serve as a strong foundation for the targeted development of drugs.
凍結剤: ETHANE / チャンバー内湿度: 90 % / 装置: GATAN CRYOPLUNGE 3 詳細: Sample was applied to a glow-discharged holey carbon grid, incubated for 10 s and manually blotted for 3 s from the backside with filter paper..
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電子顕微鏡法
顕微鏡
FEI TITAN KRIOS
詳細
Cs corrected microscope
撮影
フィルム・検出器のモデル: FEI FALCON II (4k x 4k) 検出モード: COUNTING / デジタル化 - 画像ごとのフレーム数: 2-8 / 平均露光時間: 0.475 sec. / 平均電子線量: 16.0 e/Å2
電子線
加速電圧: 300 kV / 電子線源: FIELD EMISSION GUN
電子光学系
最大 デフォーカス(補正後): 2.6 µm / 最小 デフォーカス(補正後): 0.8 µm / 照射モード: OTHER / 撮影モード: BRIGHT FIELD / 倍率(公称値): 59000