[ak-tuh
n] 
| a globulin that is present in muscle plasma and that in connection with myosin plays an important role in muscle contraction. |
| var. of actino- before a vowel: actinism. |
| a combining form with the meaning “ray, beam,” used in the formation of compound words, with the particular senses “radiation” in the physical sciences (actinometer) and “having raylike structures,” “radiate in form” in biology (actinomyces; actinopod). |
| ac·tin (āk'tĭn) n. A protein found in muscle that together with myosin functions in muscle contraction. [Latin āctus, motion; see act + -in.] |
actin ac·tin (āk'tĭn)
n.
One of the protein components found in muscle, existing as F-actin or G-actin, into which actomyosin can be split and which acts with myosin in muscle contraction.
actino- or actin-
pref.
Actinic radiation: actinotherapy.
s