Actin

//ˈæktɪn// noun

noun ·Rare ·Advanced level

Definitions

Noun
  1. 1
    A globular structural protein that polymerizes in a helical fashion to form an actin filament (or microfilament). uncountable

    "2012, Elaine N. Marieb & Katja Hoehn, Human Anatomy & Physiology, 8th ed., chapter 9 "Muscles and Muscle Tissue", page 281. Actin has kidney-shaped polypeptide subunits, called globular actin or G actin, which bear the active sites to which the myosin heads attach during contraction."

  2. 2
    one of the proteins into which actomyosin can be split; can exist in either a globular or a fibrous form wordnet
  3. 3
    One of the six isoforms of actin. countable

Example

More examples

"Actin is a protein very important to the health of a cell."

Etymology

From Ancient Greek ἀκτίς (aktís, “ray”), based on the shape of the filament formed, + -in.

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.