Bovine Cardiac Troponin T: Amino Acid Sequences of the Two Isoforms

John Leszyk, John H. Collins, Ranjana Dumaswala, James D. Potter, Nikolai B. Gusev, Alexander Dmitriyevich Verin, Larry S. Tobacman

Research output: Contribution to journalArticle

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Abstract

Troponin T (TnT) is the tropomyosin-binding subunit of troponin, the thin filament regulatory complex that confers calcium sensitivity to striated muscle contraction and actomyosin ATPase activity. Bovine cardiac muscle contains two isoforms (TnT-1 and TnT-2) of TnT that differ in sequence near their amino termini. Thin filaments containing TnT-2 require less calcium to activate the MgATPase rate of myosin than do thin filaments containing TnT-1. Using whole troponin T purified from adult bovine cardiac muscle, we have determined the complete amino acid sequence of the larger, more abundant isoform TnT-1. We confirmed that sequence differences between TnT-1 and TnT-2 are confined to the amino-terminal regions and found that TnT-1 makes up approximately 75% of the total troponin T isolated. Partial sequencing of the separated isoforms showed that the difference between them is due solely to residues 15–19 (Glu-Ala-Ala-Glu-Glu) of TnT-1 being absent from TnT-2. The deleted segment may correspond to the product of exon 4 of the chicken cardiac TnT gene [Cooper, T.A., & Ordahl, C.P. (1985) J. Biol. Chem. 260, 11140–11148]. Exon 5, which is developmentally regulated in the chicken, is not expressed in either TnT-1 or TnT-2. TnT-1 contains 284 amino acid residues and has a Mr of 33 808, while TnT-2 contains 279 amino acid residues and has a Mr of 33 279. Bovine cardiac TnT contains the only known thiol group in any isolated TnT (Cys-39 of TnT-1, Cys-34 of TnT-2). Comparison of bovine, rabbit, and chicken cardiac TnT sequences shows near identity of the amino-terminal 13 amino acid residues (exons 2 and 3 of the chicken cardiac gene), many differences in the following 60 residues (exons 4–8), and great similarity in the C-terminal 230 residues (exons 9–18).

Original languageEnglish (US)
Pages (from-to)7035-7042
Number of pages8
JournalBiochemistry
Volume26
Issue number22
DOIs
StatePublished - Jan 1 1987
Externally publishedYes

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Troponin T
Amino Acid Sequence
Protein Isoforms
Amino Acids
Exons
Chickens
Muscle
Myosins
Myocardium
Genes

ASJC Scopus subject areas

  • Biochemistry

Cite this

Leszyk, J., Collins, J. H., Dumaswala, R., Potter, J. D., Gusev, N. B., Verin, A. D., & Tobacman, L. S. (1987). Bovine Cardiac Troponin T: Amino Acid Sequences of the Two Isoforms. Biochemistry, 26(22), 7035-7042. https://doi.org/10.1021/bi00396a027

Bovine Cardiac Troponin T : Amino Acid Sequences of the Two Isoforms. / Leszyk, John; Collins, John H.; Dumaswala, Ranjana; Potter, James D.; Gusev, Nikolai B.; Verin, Alexander Dmitriyevich; Tobacman, Larry S.

In: Biochemistry, Vol. 26, No. 22, 01.01.1987, p. 7035-7042.

Research output: Contribution to journalArticle

Leszyk, J, Collins, JH, Dumaswala, R, Potter, JD, Gusev, NB, Verin, AD & Tobacman, LS 1987, 'Bovine Cardiac Troponin T: Amino Acid Sequences of the Two Isoforms', Biochemistry, vol. 26, no. 22, pp. 7035-7042. https://doi.org/10.1021/bi00396a027
Leszyk J, Collins JH, Dumaswala R, Potter JD, Gusev NB, Verin AD et al. Bovine Cardiac Troponin T: Amino Acid Sequences of the Two Isoforms. Biochemistry. 1987 Jan 1;26(22):7035-7042. https://doi.org/10.1021/bi00396a027
Leszyk, John ; Collins, John H. ; Dumaswala, Ranjana ; Potter, James D. ; Gusev, Nikolai B. ; Verin, Alexander Dmitriyevich ; Tobacman, Larry S. / Bovine Cardiac Troponin T : Amino Acid Sequences of the Two Isoforms. In: Biochemistry. 1987 ; Vol. 26, No. 22. pp. 7035-7042.
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abstract = "Troponin T (TnT) is the tropomyosin-binding subunit of troponin, the thin filament regulatory complex that confers calcium sensitivity to striated muscle contraction and actomyosin ATPase activity. Bovine cardiac muscle contains two isoforms (TnT-1 and TnT-2) of TnT that differ in sequence near their amino termini. Thin filaments containing TnT-2 require less calcium to activate the MgATPase rate of myosin than do thin filaments containing TnT-1. Using whole troponin T purified from adult bovine cardiac muscle, we have determined the complete amino acid sequence of the larger, more abundant isoform TnT-1. We confirmed that sequence differences between TnT-1 and TnT-2 are confined to the amino-terminal regions and found that TnT-1 makes up approximately 75{\%} of the total troponin T isolated. Partial sequencing of the separated isoforms showed that the difference between them is due solely to residues 15–19 (Glu-Ala-Ala-Glu-Glu) of TnT-1 being absent from TnT-2. The deleted segment may correspond to the product of exon 4 of the chicken cardiac TnT gene [Cooper, T.A., & Ordahl, C.P. (1985) J. Biol. Chem. 260, 11140–11148]. Exon 5, which is developmentally regulated in the chicken, is not expressed in either TnT-1 or TnT-2. TnT-1 contains 284 amino acid residues and has a Mr of 33 808, while TnT-2 contains 279 amino acid residues and has a Mr of 33 279. Bovine cardiac TnT contains the only known thiol group in any isolated TnT (Cys-39 of TnT-1, Cys-34 of TnT-2). Comparison of bovine, rabbit, and chicken cardiac TnT sequences shows near identity of the amino-terminal 13 amino acid residues (exons 2 and 3 of the chicken cardiac gene), many differences in the following 60 residues (exons 4–8), and great similarity in the C-terminal 230 residues (exons 9–18).",
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N2 - Troponin T (TnT) is the tropomyosin-binding subunit of troponin, the thin filament regulatory complex that confers calcium sensitivity to striated muscle contraction and actomyosin ATPase activity. Bovine cardiac muscle contains two isoforms (TnT-1 and TnT-2) of TnT that differ in sequence near their amino termini. Thin filaments containing TnT-2 require less calcium to activate the MgATPase rate of myosin than do thin filaments containing TnT-1. Using whole troponin T purified from adult bovine cardiac muscle, we have determined the complete amino acid sequence of the larger, more abundant isoform TnT-1. We confirmed that sequence differences between TnT-1 and TnT-2 are confined to the amino-terminal regions and found that TnT-1 makes up approximately 75% of the total troponin T isolated. Partial sequencing of the separated isoforms showed that the difference between them is due solely to residues 15–19 (Glu-Ala-Ala-Glu-Glu) of TnT-1 being absent from TnT-2. The deleted segment may correspond to the product of exon 4 of the chicken cardiac TnT gene [Cooper, T.A., & Ordahl, C.P. (1985) J. Biol. Chem. 260, 11140–11148]. Exon 5, which is developmentally regulated in the chicken, is not expressed in either TnT-1 or TnT-2. TnT-1 contains 284 amino acid residues and has a Mr of 33 808, while TnT-2 contains 279 amino acid residues and has a Mr of 33 279. Bovine cardiac TnT contains the only known thiol group in any isolated TnT (Cys-39 of TnT-1, Cys-34 of TnT-2). Comparison of bovine, rabbit, and chicken cardiac TnT sequences shows near identity of the amino-terminal 13 amino acid residues (exons 2 and 3 of the chicken cardiac gene), many differences in the following 60 residues (exons 4–8), and great similarity in the C-terminal 230 residues (exons 9–18).

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