actin actin /ˈæktɪn/

noun

1. One of the proteins into which actomyosin can be split; can exist in either a globular or a fibrous form  ( actin )
   one of the proteins into which actomyosin can be split; can exist in either a globular or a fibrous form
    Muscle contractions involve interactions between actin and myosin proteins.
   Muscle contractions involve interactions between actin and myosin proteins.