Key result
MgATP2- radically alters cardiac and skeletal myosin micro-mechanics to generate a viscoelastic fluid.
ATP induces distinct micro-viscoelastic reconfigurations in cardiac versus skeletal myosin solutions, providing insights into the fundamental micro-scale mechanics of muscle cells.
ATP-induced viscoelastic shifts in cardiac myosin merit biophysical modeling; leaves open translation to human myocardial function.
We study the high-frequency, micro-mechanical response of suspensions composed of cardiac and skeletal muscle myosin by optical trapping interferometry. We observe that in low ionic strength solutions, upon the addition of magnesium adenosine triphosphate (MgATP2−), myosin suspensions radically change their micro-mechanics properties, generating a viscoelastic fluid characterized by a complex modulus similar to a suspension of worm-like micelles. This transduction of energy, from chemical to mechanical, may be related to the relaxed states of myosin, which regulate muscle contractility and can be involved in the etiology of many myopathies. Within an analogous generic mechanical response, cardiac and skeletal myosin suspensions provide different stress relaxation times, elastic modulus values, and characteristic lengths. These discrepancies probably rely on the dissimilar physiological functions of cardiac and skeletal muscle, on the different MgATPase hydrolysis rates of cardiac and skeletal myosins, and on the observed distinct cooperative behavior of their myosin heads in the super-relaxed state. In vitro studies like these allow us to understand the foundations of muscle cell mechanics on the micro-scale, and may contribute to the engineering of biological materials whose micro-mechanics can be activated by energy regulators.
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Domínguez-García et al. (2024) studied Cardiac and skeletal muscle myosin suspensions. Magnesium adenosine triphosphate (MgATP2−) was evaluated on High-frequency, micro-mechanical response (stress relaxation times, elastic modulus values, and characteristic lengths). Addition of MgATP2- to cardiac and skeletal myosin suspensions radically changed their micro-mechanics properties, generating a viscoelastic fluid with distinct stress relaxation times.
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