Mapping the functional domains within the carboxyl terminus of α-tropomyosin encoded by the alternatively spliced ninth exon

Robin L. Hammell, Sarah Hitchcock

Research output: Contribution to journalArticle

73 Citations (Scopus)

Abstract

Tropomyosins are highly conserved, coiled-coil actin binding proteins found in most eukaryotic cells. Striated and smooth muscle α-tropomyosins differ by the regions encoded by exons 2 and 9. Unacetylated smooth tropomyosin expressed in Escherichia coli binds actin with high affinity, whereas unacetylated striated tropomyosin requires troponin, found only in striated muscle, for strong actin binding. The residues encoded by exon 9 cause these differences (Cho, Y.-J., and Hitchcock-De-Gregori, S. E. (1991) Proc. Natl. Acad. Sci. U. S. A. 88, 10153-10157). We mapped the functional domains encoded by the α-tropomyosin exon 9a (striated muscle-specific) and 9d (constitutively expressed), by measuring actin binding and regulation of the actomyosin MgATPase by tropomyosin exon 9 chimeras and truncation mutants expressed in E. coli. We have shown that: 1) the carboxyl-terminal nine residues define the actin affinity of unacetylated tropomyosin; 2) in the presence of Ca2+, the entire exon 9a is required for troponin to promote fully high affinity actin binding; 3) the first 18 residues encoded by exon 9a are critical for the interaction of troponin with tropomyosin on the thin filament, even in the absence of Ca2+. The results give new insight into the structural requirements of tropomyosin for thin filament assembly and regulatory function.

Original languageEnglish (US)
Pages (from-to)4236-4242
Number of pages7
JournalJournal of Biological Chemistry
Volume271
Issue number8
DOIs
StatePublished - Feb 23 1996

Fingerprint

Tropomyosin
Exons
Actins
Troponin
Striated Muscle
Muscle
Escherichia coli
Microfilament Proteins
Actomyosin
Eukaryotic Cells
Smooth Muscle

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Biochemistry
  • Cell Biology

Cite this

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title = "Mapping the functional domains within the carboxyl terminus of α-tropomyosin encoded by the alternatively spliced ninth exon",
abstract = "Tropomyosins are highly conserved, coiled-coil actin binding proteins found in most eukaryotic cells. Striated and smooth muscle α-tropomyosins differ by the regions encoded by exons 2 and 9. Unacetylated smooth tropomyosin expressed in Escherichia coli binds actin with high affinity, whereas unacetylated striated tropomyosin requires troponin, found only in striated muscle, for strong actin binding. The residues encoded by exon 9 cause these differences (Cho, Y.-J., and Hitchcock-De-Gregori, S. E. (1991) Proc. Natl. Acad. Sci. U. S. A. 88, 10153-10157). We mapped the functional domains encoded by the α-tropomyosin exon 9a (striated muscle-specific) and 9d (constitutively expressed), by measuring actin binding and regulation of the actomyosin MgATPase by tropomyosin exon 9 chimeras and truncation mutants expressed in E. coli. We have shown that: 1) the carboxyl-terminal nine residues define the actin affinity of unacetylated tropomyosin; 2) in the presence of Ca2+, the entire exon 9a is required for troponin to promote fully high affinity actin binding; 3) the first 18 residues encoded by exon 9a are critical for the interaction of troponin with tropomyosin on the thin filament, even in the absence of Ca2+. The results give new insight into the structural requirements of tropomyosin for thin filament assembly and regulatory function.",
author = "Hammell, {Robin L.} and Sarah Hitchcock",
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Mapping the functional domains within the carboxyl terminus of α-tropomyosin encoded by the alternatively spliced ninth exon. / Hammell, Robin L.; Hitchcock, Sarah.

In: Journal of Biological Chemistry, Vol. 271, No. 8, 23.02.1996, p. 4236-4242.

Research output: Contribution to journalArticle

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T1 - Mapping the functional domains within the carboxyl terminus of α-tropomyosin encoded by the alternatively spliced ninth exon

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AU - Hitchcock, Sarah

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N2 - Tropomyosins are highly conserved, coiled-coil actin binding proteins found in most eukaryotic cells. Striated and smooth muscle α-tropomyosins differ by the regions encoded by exons 2 and 9. Unacetylated smooth tropomyosin expressed in Escherichia coli binds actin with high affinity, whereas unacetylated striated tropomyosin requires troponin, found only in striated muscle, for strong actin binding. The residues encoded by exon 9 cause these differences (Cho, Y.-J., and Hitchcock-De-Gregori, S. E. (1991) Proc. Natl. Acad. Sci. U. S. A. 88, 10153-10157). We mapped the functional domains encoded by the α-tropomyosin exon 9a (striated muscle-specific) and 9d (constitutively expressed), by measuring actin binding and regulation of the actomyosin MgATPase by tropomyosin exon 9 chimeras and truncation mutants expressed in E. coli. We have shown that: 1) the carboxyl-terminal nine residues define the actin affinity of unacetylated tropomyosin; 2) in the presence of Ca2+, the entire exon 9a is required for troponin to promote fully high affinity actin binding; 3) the first 18 residues encoded by exon 9a are critical for the interaction of troponin with tropomyosin on the thin filament, even in the absence of Ca2+. The results give new insight into the structural requirements of tropomyosin for thin filament assembly and regulatory function.

AB - Tropomyosins are highly conserved, coiled-coil actin binding proteins found in most eukaryotic cells. Striated and smooth muscle α-tropomyosins differ by the regions encoded by exons 2 and 9. Unacetylated smooth tropomyosin expressed in Escherichia coli binds actin with high affinity, whereas unacetylated striated tropomyosin requires troponin, found only in striated muscle, for strong actin binding. The residues encoded by exon 9 cause these differences (Cho, Y.-J., and Hitchcock-De-Gregori, S. E. (1991) Proc. Natl. Acad. Sci. U. S. A. 88, 10153-10157). We mapped the functional domains encoded by the α-tropomyosin exon 9a (striated muscle-specific) and 9d (constitutively expressed), by measuring actin binding and regulation of the actomyosin MgATPase by tropomyosin exon 9 chimeras and truncation mutants expressed in E. coli. We have shown that: 1) the carboxyl-terminal nine residues define the actin affinity of unacetylated tropomyosin; 2) in the presence of Ca2+, the entire exon 9a is required for troponin to promote fully high affinity actin binding; 3) the first 18 residues encoded by exon 9a are critical for the interaction of troponin with tropomyosin on the thin filament, even in the absence of Ca2+. The results give new insight into the structural requirements of tropomyosin for thin filament assembly and regulatory function.

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