Characterization of paramyosin and thin filaments in the smooth muscle of acorn worm, a member of hemichordates

Hiroki Sonobe, Takashi Obinata, Takuya Minokawa, Tomohiro Haruta, Yuuki Kawamura, Shinryu Wakatsuki, Naruki Sato

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Paramyosin is a myosin-binding protein characteristic of invertebrate animals, while troponin is a Ca2+-dependent regulator of muscle contraction. Both proteins are widely distributed in protostomes, while in deuterostomes, their distribution is limited; namely, presence of paramyosin and absence of troponin are common features in echinoderm muscles, while muscles of chordates contain troponin but lack paramyosin. In this study, we examined the muscle of a hemichordate, acorn worm, to clarify whether this animal is like echinoderms or like the other deuterostome animals. We found a 100-kDa protein in the smooth muscle of acorn worm. This protein was identified with paramyosin, since the purified protein formed paracrystals with a constant axial periodicity in the presence of divalent cations as paramyosin of other animals, showed ability to interact with myosin and shared common antigenicity with echinoderm paramyosin. On the other hand, troponin band was not detected in isolated thin filaments, and the filaments increased myosin-ATPase activity in a Ca2+-independent manner. The results indicate that troponin is lacking in thin filaments of acorn worm muscle just as in those of echinoderms. The muscle of hemichordate acorn worm is quite similar to echinoderm muscles, but different from chordate muscles.

Original languageEnglish
Pages (from-to)369-379
Number of pages11
JournalJournal of biochemistry
Issue number6
Publication statusPublished - 2016 Dec


  • Balanoglossus misakiensis
  • Hemichordate
  • Muscle proteins
  • Paramyosin
  • Troponin

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology


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