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Cryo-electron tomography of cardiac myofibrils reveals a 3D lattice spring within the Z-discs.

ABSTRACT: The Z-disc forms a boundary between sarcomeres, which constitute structural and functional units of striated muscle tissue. Actin filaments from adjacent sarcomeres are cross-bridged by ?-actinin in the Z-disc, allowing transmission of tension across the myofibril. Despite decades of studies, the 3D structure of Z-disc has remained elusive due to the limited resolution of conventional electron microscopy. Here, we observed porcine cardiac myofibrils using cryo-electron tomography and reconstructed the 3D structures of the actin-actinin cross-bridging complexes within the Z-discs in relaxed and activated states. We found that the ?-actinin dimers showed contraction-dependent swinging and sliding motions in response to a global twist in the F-actin lattice. Our observation suggests that the actin-actinin complex constitutes a molecular lattice spring, which maintains the integrity of the Z-disc during the muscle contraction cycle.

SUBMITTER: Oda T

PROVIDER: S-EPMC7567829 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Cryo-electron tomography of cardiac myofibrils reveals a 3D lattice spring within the Z-discs.

Oda Toshiyuki T Yanagisawa Haruaki H

Communications biology 20201016 1

The Z-disc forms a boundary between sarcomeres, which constitute structural and functional units of striated muscle tissue. Actin filaments from adjacent sarcomeres are cross-bridged by α-actinin in the Z-disc, allowing transmission of tension across the myofibril. Despite decades of studies, the 3D structure of Z-disc has remained elusive due to the limited resolution of conventional electron microscopy. Here, we observed porcine cardiac myofibrils using cryo-electron tomography and reconstruct ...[more]

PMID: 33067529

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