Cardiac muscle thin filament structures reveal calcium regulatory mechanism

Author:

Yamada YurikaORCID,Namba KeiichiORCID,Fujii TakashiORCID

Abstract

AbstractContraction of striated muscles is driven by cyclic interactions of myosin head projecting from the thick filament with actin filament and is regulated by Ca2+released from sarcoplasmic reticulum. Muscle thin filament consists of actin, tropomyosin and troponin, and Ca2+binding to troponin triggers conformational changes of troponin and tropomyosin to allow actin-myosin interactions. However, the structural changes involved in this regulatory mechanism remain unknown. Here we report the structures of human cardiac muscle thin filament in the absence and presence of Ca2+by electron cryomicroscopy. Molecular models in the two states built based on available crystal structures reveal the structures of a C-terminal region of troponin I and an N-terminal region of troponin T in complex with the head-to-tail junction of tropomyosin together with the troponin core on actin filament. Structural changes of the thin filament upon Ca2+binding now reveal the mechanism of Ca2+regulation of muscle contraction.

Funder

MEXT | Japan Society for the Promotion of Science

Japan Agency for Medical Research and Development

JEOL YOKOGUSHI Research Alliance Laboratories of Osaka University

MEXT | JST | Precursory Research for Embryonic Science and Technology

Publisher

Springer Science and Business Media LLC

Subject

General Physics and Astronomy,General Biochemistry, Genetics and Molecular Biology,General Chemistry

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