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Related Concept Videos

Actin and Myosin in Muscle Contraction01:16

Actin and Myosin in Muscle Contraction

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Actin and myosin are contractile proteins that form the sarcomere found in skeletal muscle tissues for regulating muscle contraction. Actin, a globular contractile protein, interacts with myosin for muscle contraction. The skeletal tissue appears striped or striated under a microscope due to the repeated arrangement of contractile proteins actin and myosin along the length of myofibrils. Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell causes...
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Phosphorylation01:02

Phosphorylation

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The addition or removal of phosphate groups from proteins is the most common chemical modification that regulates cellular processes. These modifications can affect the structure, activity, stability, and localization of proteins within cells as well as their interactions with other proteins.
During phosphorylation, protein kinases transfer the terminal phosphate group of ATP to specific amino acid side chains of substrate proteins. Serine, threonine, and tyrosine are the most commonly...
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Overview of Myosin Structure and Function01:15

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Myosins are a family of molecular motor proteins, first identified in the skeletal muscles, where they are responsible for muscle contraction. Along with their role in muscle contraction, these proteins also play a role in the intracellular transport of molecules and vesicles. There are twenty-four classes of myosins based on their domain sequence and organization. Of the twenty-four, six classes (Myosin I, Myosin II, Myosin V, Myosin VI, Myosin VII, and Myosin X)  have been well...
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Protein Kinases and Phosphatases02:54

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Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
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The Role of Actin and Myosin in Non-muscle Cells01:10

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Actin and myosin or actomyosin filaments also play a significant role in cells other than those involved in muscle contraction (which occurs within the sarcomere of muscle cells). The mechanism of non-muscle cell contractile bundles was first observed in Dictyostelium and Acanthamoeba. In non-muscle cells, two bundles are commonly found: stress fibers and actomyosin adherence belts. These contractile bundles are smaller and less organized than the ones found in muscle cells. They  are held...
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Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
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Ventricular myosin modifies in vitro step-size when phosphorylated.

Yihua Wang1, Katalin Ajtai1, Thomas P Burghardt2

  • 1Department of Biochemistry and Molecular Biology, United States.

Journal of Molecular and Cellular Cardiology
|April 15, 2014
PubMed
Summary

Phosphorylation of regulatory light chains (RLC) in cardiac myosin significantly increases myosin step-size. This enhances mechanical work per cycle, revealing a novel contraction regulation mechanism.

Keywords:
Actin-activated ATPaseCardiac myosin RLC phosphorylationIn vitro motilityQdot assayVentricular myosin step-size

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Area of Science:

  • Muscle physiology
  • Biochemistry
  • Molecular biology

Background:

  • Cardiac and skeletal muscle contraction rely on myosin's motor domain to convert ATP energy into mechanical work.
  • Myosin's lever-arm, stabilized by light chains, dictates the step-size of actin movement.
  • Regulatory light chain (RLC) phosphorylation at S15 influences myosin mechanics and muscle response to disease.

Purpose of the Study:

  • To investigate the effect of S15 phosphorylation on the step-size distribution of beta-cardiac myosin (βMys).
  • To determine how RLC phosphorylation modulates the mechanical characteristics and work output of cardiac myosin.

Main Methods:

  • Utilized a novel quantum dot (Qdot) assay to measure myosin step-size.
  • Compared step-size distributions for phosphorylated and unphosphorylated βMys.

Main Results:

  • Unphosphorylated βMys exhibited multiple step-sizes (5nm, 8nm, rare 3nm).
  • S15 phosphorylation in βMys shifted the distribution, making the 8nm step dominant.
  • Phosphorylation significantly increased the average myosin step-size and work produced per ATPase cycle.

Conclusions:

  • RLC phosphorylation at S15 is a key regulator of cardiac myosin step-size.
  • Modulation of step-size by phosphorylation impacts work production, suggesting a myosin filament-based contraction regulation mechanism.