8V01

The structure of the native cardiac thin filament troponin core in Ca2+-bound fully activated state 1 from the lower strand

8V01 の概要

• エントリーDOI: 10.2210/pdb8v01/pdb
• EMDBエントリー: 42849
• 分子名称: Actin, alpha cardiac muscle 1, Troponin C, slow skeletal and cardiac muscles, Troponin I, cardiac muscle, ... (8 entities in total)
• 機能のキーワード: thin filament, troponin, tropomyosin, cryo-em, muscle structure, motor protein
• 由来する生物種: Sus scrofa (pig); 詳細
• タンパク質・核酸の鎖数: 7
• 化学式量合計: 227146.27

構造登録者

Galkin, V.E.,Risi, C.M. (登録日: 2023-11-16, 公開日: 2024-03-06, 最終更新日: 2024-03-13)

主引用文献

Risi, C.M.,Belknap, B.,Atherton, J.,Coscarella, I.L.,White, H.D.,Bryant Chase, P.,Pinto, J.R.,Galkin, V.E.
Troponin Structural Dynamics in the Native Cardiac Thin Filament Revealed by Cryo Electron Microscopy.
J.Mol.Biol., 436:168498-168498, 2024

PubMed Abstract: Cardiac muscle contraction occurs due to repetitive interactions between myosin thick and actin thin filaments (TF) regulated by Ca levels, active cross-bridges, and cardiac myosin-binding protein C (cMyBP-C). The cardiac TF (cTF) has two nonequivalent strands, each comprised of actin, tropomyosin (Tm), and troponin (Tn). Tn shifts Tm away from myosin-binding sites on actin at elevated Ca levels to allow formation of force-producing actomyosin cross-bridges. The Tn complex is comprised of three distinct polypeptides - Ca-binding TnC, inhibitory TnI, and Tm-binding TnT. The molecular mechanism of their collective action is unresolved due to lack of comprehensive structural information on Tn region of cTF. C1 domain of cMyBP-C activates cTF in the absence of Ca to the same extent as rigor myosin. Here we used cryo-EM of native cTFs to show that cTF Tn core adopts multiple structural conformations at high and low Ca levels and that the two strands are structurally distinct. At high Ca levels, cTF is not entirely activated by Ca but exists in either partially or fully activated state. Complete dissociation of TnI C-terminus is required for full activation. In presence of cMyBP-C C1 domain, Tn core adopts a fully activated conformation, even in absence of Ca. Our data provide a structural description for the requirement of myosin to fully activate cTFs and explain increased affinity of TnC to Ca in presence of active cross-bridges. We suggest that allosteric coupling between Tn subunits and Tm is required to control actomyosin interactions.

PubMed: 38387550
DOI: 10.1016/j.jmb.2024.168498

実験手法

ELECTRON MICROSCOPY (5.5 Å)