Journal article
The role of tropomyosin isoforms and phosphorylation in force generation in thin-filament reconstituted bovine cardiac muscle fibres
Journal of muscle research and cell motility, Vol.31(2), pp.93-109
08/01/2010
DOI: 10.1007/s10974-010-9213-x
PMCID: PMC3089900
PMID: 20559861
Abstract
The thin filament extraction and reconstitution protocol was used to investigate the functional roles of tropomyosin (Tm) isoforms and phosphorylation in bovine myocardium. The thin filament was extracted by gelsolin, reconstituted with G-actin, and further reconstituted with cardiac troponin together with one of three Tm varieties: phosphorylated alpha Tm (alpha Tm.P), dephosphorylated alpha Tm (alpha Tm.deP), and dephosphorylated beta Tm (beta Tm.deP). The effects of Ca, phosphate, MgATP and MgADP concentrations were examined in the reconstituted fibres at pH 7.0 and 25A degrees C. Our data show that Ca2+ sensitivity (pCa(50): half saturation point) was increased by 0.19 +/- A 0.07 units when beta Tm.deP was used instead of alpha Tm.deP (P < 0.05), and by 0.27 +/- A 0.06 units when phosphorylated alpha Tm was used (P < 0.005). The cooperativity (Hill factor) decreased (but insignificantly) from 3.2 +/- A 0.3 (5) to 2.8 +/- A 0.2 (7) with phosphorylation. The cooperativity decreased significantly from 3.2 +/- A 0.3 (5) to 2.1 +/- A 0.2 (9) with isoform change from alpha Tm.deP to beta Tm.deP. There was no significant difference in isometric tension or stiffness between alpha Tm.P, alpha Tm.deP, and beta Tm.deP muscle fibres at saturating [Ca2+] or after rigor induction. Based on the six-state cross-bridge model, sinusoidal analysis indicated that the equilibrium constants of elementary steps differed up to 1.7x between alpha Tm.deP and beta Tm.deP, and up to 2.0x between alpha Tm.deP and alpha Tm.P. The rate constants differed up to 1.5x between alpha Tm.deP and beta Tm.deP, and up to 2.4x between alpha Tm.deP and alpha Tm.P. We conclude that tension and stiffness per cross-bridge are not significantly different among the three muscle models.
Details
- Title: Subtitle
- The role of tropomyosin isoforms and phosphorylation in force generation in thin-filament reconstituted bovine cardiac muscle fibres
- Creators
- Xiaoying Lu - University of IowaDavid H. Heeley - Memorial University of NewfoundlandLawrence B. Smillie - University of AlbertaMasataka Kawai - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of muscle research and cell motility, Vol.31(2), pp.93-109
- DOI
- 10.1007/s10974-010-9213-x
- PMID
- 20559861
- PMCID
- PMC3089900
- NLM abbreviation
- J Muscle Res Cell Motil
- ISSN
- 0142-4319
- eISSN
- 1573-2657
- Publisher
- Springer Nature
- Number of pages
- 17
- Grant note
- HL70041 / NIH; United States Department of Health & Human Services; National Institutes of Health (NIH) - USA R01HL070041 / NATIONAL HEART, LUNG, AND BLOOD INSTITUTE; United States Department of Health & Human Services; National Institutes of Health (NIH) - USA; NIH National Heart Lung & Blood Institute (NHLBI) 0850184Z; 0320083Z; 0520084Z / AHA; American Heart Association Heart and Stroke Foundation of Canada; Heart & Stroke Foundation of Canada Canadian Institutes of Health Research (C.I.H.R.); Canadian Institutes of Health Research (CIHR)
- Language
- English
- Date published
- 08/01/2010
- Academic Unit
- Anatomy and Cell Biology; Internal Medicine
- Record Identifier
- 9984284344402771
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