Filamin isoforms in molluscan smooth muscle

► Three proteins from catch muscle were identified as homologous to mammalian filamin. ► FLN-270 and FLN-230 show structural differences at the rod 2 segment. ► FLN-270 but not FLN-230 was phosphorylated in vitro by PKA. ► FLN-230 was the predominant isoform in catch muscle. ► A protein identified as the mussel calponin-like protein copurified with FLN-270.