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Related Concept Videos

Actin and Myosin in Muscle Contraction01:16

Actin and Myosin in Muscle Contraction

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...
Overview of Myosin Structure and Function01:15

Overview of Myosin Structure and Function

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 characterized.
The Role of Actin and Myosin in Non-muscle Cells01:10

The Role of Actin and Myosin in Non-muscle Cells

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...
Actin Polymerization01:42

Actin Polymerization

Actin polymerization occurs through the head-to-tail association of binding sites on monomeric actin or G-actin to form filamentous or F-actin. The polymerization can be divided into three phases ̶  nucleation, elongation, and steady-state phase.
The nucleation phase involves forming a stable nucleus consisting of three actin monomers to form a new actin filament. Actin-binding proteins such as formins and Arp2/3 complex help filament growth post-nucleation. The Formins form straight actin...
Introduction to Actin01:26

Introduction to Actin

Actin is a highly conserved cytoskeletal protein found abundantly in eukaryotic cells. It constitutes 10% weight of the total cellular protein in muscle cells, while in non-muscle cells, it is lower and makes up around 1–5 percent of the total cell protein. Actin found in the unicellular amoebae and complex multicellular animals is around 80% similar, demonstrating their conservation over a billion years of evolution.  Actin coding genes are conserved within species and across different species.
ATP Synthase: Mechanism01:48

ATP Synthase: Mechanism

In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear genome encodes the majority of ATP synthase subunits, the mitochondrial genome encodes some of the enzyme's most critical components. The formation of this multi-subunit enzyme is a complex multi-step process regulated at the level of transcription, translation, and assembly. Defects in one or more of these steps can result in decreased ATP...

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Related Experiment Video

Updated: Jun 19, 2026

A Semi-High-Throughput Adaptation of the NADH-Coupled ATPase Assay for Screening Small Molecule Inhibitors
10:28

A Semi-High-Throughput Adaptation of the NADH-Coupled ATPase Assay for Screening Small Molecule Inhibitors

Published on: August 17, 2019

A STUDY OF THE ADENOSINE TRIPHOSPHATASE ACTIVITY OF MYOSIN AND ACTOMYOSIN.

W F Mommaerts1, K Seraidarian

  • 1Department of Biological Chemistry, The American University of Beirut, Beirut, Lebanon.

The Journal of General Physiology
|October 30, 2009
PubMed
Summary
This summary is machine-generated.

Myosin-adenosine triphosphatase (ATPase) activity is activated by salts like KCl and CaCl(2) but inhibited by MgCl(2). This enzyme

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Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers
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Published on: May 4, 2022

Area of Science:

  • Biochemistry
  • Muscle Physiology

Background:

  • Adenosine triphosphatase (ATPase) activity is crucial for muscle contraction.
  • Myosin and actomyosin are key proteins involved in muscle function.

Purpose of the Study:

  • To investigate the enzymatic activity of myosin-ATPase under various conditions.
  • To determine the role of myosin-ATPase in muscle metabolism.

Main Methods:

  • Experimental study of crystalline myosin and actomyosin preparations.
  • Assay of ATPase activity under different salt concentrations, pH levels, and ion ratios (Mg-Ca antagonism).

Main Results:

  • Enzymatic activity requires salts; KCl and CaCl(2) activate, while MgCl(2) inhibits.
  • pH optima exist at 6.2-6.5 and 9.2 with Ca(2+), and only at 6.2-6.5 without Ca(2+).
  • Mg(2+) significantly inhibits activity, especially at Mg:Ca ratios below 1.

Conclusions:

  • Myosin-ATPase activity in vitro is significantly lower than the inorganic phosphate liberation rate observed during muscle activity.
  • Myosin-ATPase is unlikely to be responsible for the primary phosphate liberation in contracting muscles.
  • The proposed role of myosin-ATPase in muscle metabolism requires re-evaluation.