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• actin
  actin

  noun

  a globulin that is present in muscle plasma and that in connection with myosin plays an important role in muscle contraction.
• actin-
  actin-

  variant of actino- before a vowel.

actin

¹ American  

[ak-tuhn] / ˈæk tən /

noun

Biochemistry.

1. a globulin that is present in muscle plasma and that in connection with myosin plays an important role in muscle contraction.

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actin- ² American  

1. variant of actino- before a vowel.

   actinism.

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actin British  

/ ˈæktɪn /

noun

1. a protein that participates in many kinds of cell movement, including muscle contraction, during which it interacts with filaments of a second protein, myosin

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actin Scientific  

/ ăk′tĭn /

1. A protein found in all eukaryotic cells, forming filaments that make up a main component of the cell's supporting matrix or cytoskeleton. Actin and the protein myosin together make up the contractile units (called sarcomeres) of skeletal muscle fibers.

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Etymology

Origin of actin

1940–45; perhaps act + -in ²

Example Sentences

See Examples For:

actin actin-

These flows move actin and other proteins toward the front of the cell much faster than diffusion alone.

From Science Daily ● Apr. 1, 2026

If the cytoplasm becomes more fluid during M-phase, how does the actin band avoid collapsing?

From Science Daily ● Feb. 28, 2026

In many organisms, cells divide by building a ring made of the protein actin at the cell's midpoint.

From Science Daily ● Feb. 28, 2026

The team also observed that microtubules, another key part of the cytoskeleton, bent and spread out when the actin band was cut.

From Science Daily ● Feb. 28, 2026

“You don’t understand. Him and State ain’t actin like they just hidin him. They actin like he did it.”

From "Song of Solomon" by Toni Morrison

Myosin heads will not detach from the actin- binding sites, resulting in muscle stiffness.

From Textbooks ● Jun. 9, 2022

Myosin heads will detach rapidly from the actin- binding sites, resulting in muscle relaxation.

From Textbooks ● Jun. 9, 2022

The Ca++ ions in the sarcoplasm have bound to troponin, tropomyosin has shifted away from actin- binding sites, cross-bridges formed, and sarcomeres are actively shortening to the point of peak tension.

From Textbooks ● Jun. 19, 2013