Characterization of two tropomyosin isoforms from the fast skeletal muscle of bluefin tuna Thunnus thynnus orientalis

Yoshihiro Ochiai, Hideo Ozawa, Ming Chih Huang, Shugo Watabe

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)


Fast skeletal muscle tropomyosin (TM) of tunas is composed of nearly equimolar amount of two isoforms designated α-TM and β-TM expediently based on their migration behavior in SDS-PAGE, whereas corresponding TMs from the other fish species are homogenous (α-type). The presence of β-TM is thus specific to tunas so far. The amino acid sequence of β-TM from bluefin tuna Thunnus thynnus orientalis, which has not been revealed to date unlike α-TM, was successfully obtained in this study by cDNA cloning. The coding region of β-TM cDNA comprised of an open reading frame of 855. bp encoding 284 amino acid residues, like most of the TMs. Unexpectedly, the sequence of β-TM showed high similarity to those of other vertebrate α-type TMs including tuna α-TM. Phylogenetic analysis also showed that β-TM has the closest relationship with α-TM of tuna. This fact was quite unlike the relation of mammalian α- and β-TMs. Based on the distribution of amino acid substitutions, it was suggested that tuna TM isoforms are the products of different genes. By thermodynamic analysis of native and reconstituted TMs, it was demonstrated that β-TM is less thermostable than α-TM. Proteolytic digestion also supported the lower stability of the former.

Original languageEnglish
Pages (from-to)96-103
Number of pages8
JournalArchives of Biochemistry and Biophysics
Issue number2
Publication statusPublished - 2010 Oct
Externally publishedYes


  • Isoform
  • Primary structure
  • Skeletal muscle
  • Thermostability
  • Tropomyosin
  • Tuna

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology


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