Tropomyosin Period 3 Is Essential for Enhancement of Isometric Tension in Thin Filament-Reconstituted Bovine Myocardium

Masataka Kawai; Xiaoying Lu; Sarah E Hitchcock-DeGregori; Kristen J Stanton; Michael W Wandling

doi:10.1155/2009/380967

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Tropomyosin Period 3 Is Essential for Enhancement of Isometric Tension in Thin Filament-Reconstituted Bovine Myocardium

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Tropomyosin Period 3 Is Essential for Enhancement of Isometric Tension in Thin Filament-Reconstituted Bovine Myocardium

Masataka Kawai, Xiaoying Lu, Sarah E Hitchcock-DeGregori, Kristen J Stanton and Michael W Wandling

Journal of Biophysics, Vol.2009, pp.380967-17

2009

DOI: 10.1155/2009/380967

PMCID: PMC2814127

PMID: 20130792

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Abstract

Tropomyosin (Tm) consists of 7 quasiequivalent repeats known as “periods,” and its specific function may be associated with these periods. To test the hypothesis that either period 2 or 3 promotes force generation by inducing a positive allosteric effect on actin, we reconstituted the thin filament with mutant Tm in which either period 2 (Δ2Tm) or period 3 (Δ3Tm) was deleted. We then studied: isometric tension, stiffness, 6 kinetic constants, and the pCa-tension relationship. N-terminal acetylation of Tm did not cause any differences. The isometric tension in Δ2Tm remained unchanged, and was reduced to ∼60% in Δ3Tm. Although the kinetic constants underwent small changes, the occupancy of strongly attached cross-bridges was not much different. The Hill factor (cooperativity) did not differ significantly between Δ2Tm (1.79 ± 0.19) and the control (1.73 ± 0.21), or Δ3Tm (1.35 ± 0.22) and the control. In contrast, pCa 50 decreased slightly in Δ2Tm (5.11 ± 0.07), and increased significantly in Δ3Tm (5.57 ± 0.09) compared to the control (5.28 ± 0.04). These results demonstrate that, when ions are present at physiological concentrations in the muscle fiber system, period 3 (but not period 2) is essential for the positive allosteric effect that enhances the interaction between actin and myosin, and increases isometric force of each cross-bridge.

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Title: Subtitle: Tropomyosin Period 3 Is Essential for Enhancement of Isometric Tension in Thin Filament-Reconstituted Bovine Myocardium
Creators: Masataka Kawai - Department of Anatomy and Cell Biology, The University of Iowa, Iowa City, IA 52242, USA
Xiaoying Lu - Department of Anatomy and Cell Biology, The University of Iowa, Iowa City, IA 52242, USA
Sarah E Hitchcock-DeGregori - Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA
Kristen J Stanton - Department of Anatomy and Cell Biology, The University of Iowa, Iowa City, IA 52242, USA
Michael W Wandling - Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA
Resource Type: Journal article
Publication Details: Journal of Biophysics, Vol.2009, pp.380967-17
DOI: 10.1155/2009/380967
PMID: 20130792
PMCID: PMC2814127
NLM abbreviation: J Biophys
ISSN: 1687-8000
eISSN: 1687-8019
Publisher: Hindawi Publishing Corporation
Grant note: DOI: 10.13039/100000002, name: National Institutes of Health, award: HL70041, AHA 0850184Z, GM26236
Language: English
Date published: 2009
Academic Unit: Anatomy and Cell Biology; Internal Medicine
Record Identifier: 9984025670502771

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