A filamin-like protein—a new component of heart myofibrils

A filamin-like protein was identified in cardiac muscle of chick and rat. It was shown that in an extract obtained from chicken cardiac muscle, 1% of the protein had the same M r (250 000–270 000) as the monomer of filamin, a high-molecular weight actin-binding protein from smooth muscle. Immunofluorescent and immunocytochemical analyses of preparations of heart myofibrils and tissue sections revealed that (a) purified antibodies against filamin specifically interacted with heart myofibrils, and (b) the filamin-like protein was localized in the Z line region of the sarcomere.