Mechanism of Catch Force: Tethering of Thick and Thin Filaments by Twitchin

<table>Force responses following release of ATP from caged ATP in permeabilized ABRM. Muscles were put into high-force rigor by activation in pCa5 and then transferred to a pCa5-rigor solution containing apyrase (0.2 mg/mL).  Calcium was then lowered to pCa <svg height="8.8500004" id="M36" style="vertical-align:-0.30096pt" version="1.1" viewbox="0 0 10.825 8.8500004" width="10.825" xmlns="http://www.w3.org/2000/svg">
<g transform="matrix(1.25,0,0,-1.25,0,8.85)">
<g transform="translate(72,-64.92)">
<text transform="matrix(1,0,0,-1,-71.95,65.27)">
<tspan style="font-size: 12.50px; " x="0" y="0">&gt;</tspan>
</text>
</g>
</g>
</svg> 8. Caged ATP (4 mM) was added 4 min before the flash and the muscle was transferred to a solution containing 1 mM MgATP <svg height="5.7874999" id="M37" style="vertical-align:-0.0pt" version="1.1" viewbox="0 0 10.825 5.7874999" width="10.825" xmlns="http://www.w3.org/2000/svg">
<g transform="matrix(1.25,0,0,-1.25,0,5.7875)">
<g transform="translate(72,-67.37)">
<text transform="matrix(1,0,0,-1,-71.95,67.42)">
<tspan style="font-size: 12.50px; " x="0" y="0">∼</tspan>
</text>
</g>
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</svg>4 s following the flash. cAMP was added at the time shown. <i>Solid line</i>, twitchin not phosphorylated; <i>dashed lines</i>, twitchin thiophosphorylated. <svg height="10.325" id="M38" style="vertical-align:-0.0pt" version="1.1" viewbox="0 0 11.225 10.325" width="11.225" xmlns="http://www.w3.org/2000/svg">
<g transform="matrix(1.25,0,0,-1.25,0,10.325)">
<g transform="translate(72,-63.74)">
<text transform="matrix(1,0,0,-1,-71.95,63.79)">
<tspan style="font-size: 12.50px; " x="0" y="0">𝑇</tspan>
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</svg> = 20 C. Reproduced from [<a href="/journals/bmri/2010/725207/#B84">84</a>] with permission.</table>

BioMed Research International

fig7

Figure 7

Figure 7: Mechanism of Catch Force: Tethering of Thick and Thin Filaments by Twitchin 