Definition of actin in English:


Syllabification: ac·tin
Pronunciation: /ˈaktən


  • A protein that forms (together with myosin) the contractile filaments of muscle cells, and is also involved in motion in other types of cells.
    More example sentences
    • Muscle contraction is dependent on two proteins, actin and myosin.
    • As the cells round up, actin and myosin moieties are being redistributed underneath the plasma membrane.
    • Striated muscle contraction is regulated by a protein complex bound to actin.


1940: from Greek aktis, aktin- 'ray' + -in1.

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