1VDJ

Solution structure of actin-binding domain of troponin in Ca2+-bound state

1VDJ の概要

• エントリーDOI: 10.2210/pdb1vdj/pdb
• 関連するPDBエントリー: 1VDI
• NMR情報: BMRB: 9500
• 分子名称: Troponin I, fast skeletal muscle (1 entity in total)
• 機能のキーワード: troponin, actin, tropomyosin, contractile protein
• 由来する生物種: Gallus gallus (chicken)
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 6139.99

構造登録者

Murakami, K.,Yumoto, F.,Ohki, S.,Yasunaga, T.,Tanokura, M.,Wakabayashi, T. (登録日: 2004-03-22, 公開日: 2005-09-06, 最終更新日: 2023-12-27)

主引用文献

Murakami, K.,Yumoto, F.,Ohki, S.,Yasunaga, T.,Tanokura, M.,Wakabayashi, T.
Structural Basis for Ca(2+)-regulated Muscle Relaxation at Interaction Sites of Troponin with Actin and Tropomyosin
J.Mol.Biol., 352:178-201, 2005

PubMed Abstract: Troponin and tropomyosin on actin filaments constitute a Ca2+-sensitive switch that regulates the contraction of vertebrate striated muscle through a series of conformational changes within the actin-based thin filament. Troponin consists of three subunits: an inhibitory subunit (TnI), a Ca2+-binding subunit (TnC), and a tropomyosin-binding subunit (TnT). Ca2+-binding to TnC is believed to weaken interactions between troponin and actin, and triggers a large conformational change of the troponin complex. However, the atomic details of the actin-binding sites of troponin have not been determined. Ternary troponin complexes have been reconstituted from recombinant chicken skeletal TnI, TnC, and TnT2 (the C-terminal region of TnT), among which only TnI was uniformly labelled with 15N and/or 13C. By applying NMR spectroscopy, the solution structures of a "mobile" actin-binding domain (approximately 6.1 kDa) in the troponin ternary complex (approximately 52 kDa) were determined. The mobile domain appears to tumble independently of the core domain of troponin. Ca2+-induced changes in the chemical shift and line shape suggested that its tumbling was more restricted at high Ca2+ concentrations. The atomic details of interactions between actin and the mobile domain of troponin were defined by docking the mobile domain into the cryo-electron microscopy (cryo-EM) density map of thin filament at low [Ca2+]. This allowed the determination of the 3D position of residue 133 of TnI, which has been an important landmark to incorporate the available information. This enabled unique docking of the entire globular head region of troponin into the thin filament cryo-EM map at a low Ca2+ concentration. The resultant atomic model suggests that troponin interacted electrostatically with actin and caused the shift of tropomyosin to achieve muscle relaxation. An important feature is that the coiled-coil region of troponin pushed tropomyosin at a low Ca2+ concentration. Moreover, the relationship between myosin and the mobile domain on actin filaments suggests that the latter works as a fail-safe latch.

PubMed: 16061251
DOI: 10.1016/j.jmb.2005.06.067

実験手法

SOLUTION NMR