Top-down targeted proteomics for deep sequencing of tropomyosin isoforms

J Proteome Res. 2013 Jan 4;12(1):187-98. doi: 10.1021/pr301054n. Epub 2012 Dec 20.


Tropomyosins (Tm) constitute a family of ubiquitous and highly conserved actin-binding proteins, playing essential roles in a variety of biological processes. Tm isoforms produced by multiple Tm encoding genes and alternatively expressed exons along with post-translational modifications (PTMs) regulate Tm function. Therefore, to gain a better understanding of the functional role of Tm, it is essential to fully characterize Tm isoforms. Herein, we developed a top-down high-resolution mass spectrometry (MS)-based targeted proteomics method for comprehensive characterization of Tm isoforms. α-Tm was identified to be the predominant isoform in swine cardiac muscle. We further characterized its sequence and localized the PTMs such as acetylation and phosphorylation as well as amino acid polymorphisms. Interestingly, we discovered a "novel" Tm isoform that does not match with any of the currently available swine Tm sequences. A deep sequencing of this isoform by top-down MS revealed an exact match with mouse β-Tm sequence, suggesting that this "novel" isoform is swine β-Tm which is 100% conserved between swine and mouse. Taken together, we demonstrated that top-down targeted proteomics provides a powerful tool for deep sequencing of Tm isoforms from genetic variations together with complete mapping of the PTM sites.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actins / genetics
  • Actins / metabolism
  • Animals
  • Cell Line
  • High-Throughput Nucleotide Sequencing
  • Mass Spectrometry*
  • Mice
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism
  • Myocardium / metabolism
  • Protein Isoforms* / genetics
  • Protein Isoforms* / metabolism
  • Protein Processing, Post-Translational
  • Proteomics
  • Swine / genetics
  • Swine / metabolism
  • Tropomyosin* / genetics
  • Tropomyosin* / metabolism


  • Actins
  • Microfilament Proteins
  • Protein Isoforms
  • Tropomyosin