Characterizations of myosin essential light chain’s N-terminal truncation mutant Δ43 in transgenic mouse papillary muscles by using tension transients in response to sinusoidal length alterations
Cross-bridge kinetics were studied at 20 °C in cardiac muscle strips from transgenic (Tg) mice expressing N-terminal 43 amino acid truncation mutation (Δ43) of myosin essential light chain (ELC), and the results were compared to those from Tg-wild type (WT) mice. Sinusoidal length changes were appli...
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Published in | Journal of muscle research and cell motility Vol. 34; no. 2; pp. 93 - 105 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Dordrecht
Springer Netherlands
01.05.2013
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Subjects | |
Online Access | Get full text |
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Summary: | Cross-bridge kinetics were studied at 20 °C in cardiac muscle strips from transgenic (Tg) mice expressing N-terminal 43 amino acid truncation mutation (Δ43) of myosin essential light chain (ELC), and the results were compared to those from Tg-wild type (WT) mice. Sinusoidal length changes were applied to activated skinned papillary muscle strips to induce tension transients, from which two exponential processes were deduced to characterize the cross-bridge kinetics. Their two rate constants were studied as functions of ATP, phosphate (Pi), ADP, and Ca
2+
concentrations to characterize elementary steps of the cross-bridge cycle consisting of six states. Our results demonstrate for the first time that the cross-bridge kinetics of Δ43 are accelerated owing to an acceleration of the rate constant
k
2
of the cross-bridge detachment step, and that the number of strongly attached cross-bridges are decreased because of a reduction of the equilibrium constant
K
4
of the force generation step. The isometric tension and stiffness of Δ43 are diminished compared to WT, but the force per cross-bridge is not changed. Stiffness measurement during rigor induction demonstrates a reduction in the stiffness in Δ43, indicating that the N-terminal extension of ELC forms an extra linkage between the myosin cross-bridge and actin. The tension
-
pCa study demonstrates that there is no Ca
2+
sensitivity change with Δ43, but the cooperativity is diminished. These results demonstrate the importance of the N-terminal extension of ELC in maintaining the myosin motor function during force generation and optimal cardiac performance. |
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ISSN: | 0142-4319 1573-2657 |
DOI: | 10.1007/s10974-013-9337-x |