Biology subjects

Narayanan, T.

Publications and source records attributed to Narayanan, T..

2 recordsLinked to original sources

bioRxiv2026

The molecular structural basis of the braking action of muscle

Skeletal muscles generate force and shortening through a structural powerstroke in actin-bound myosin motors linked to ATP hydrolysis, but they also act as brakes to resist stretching by an external load. The molecular structural basis of muscle braking has remained obscure. Here we show that muscle braking is driven both by structural changes in myosin motors and by distortion of the lattice of thick and thin filaments including their M-band and Z-disk connections. A strained motor conformation is established early during stretch, but force continues to increase as thin filaments are displaced from their symmetrical lattice positions, the lateral shear between thick filaments increases, and the lattice volume decreases. Moreover, whilst the motor conformation rapidly recovers after the stretch, the distortion of the filament lattice is largely maintained, storing the work done on the muscle during stretch and accounting for the residual force enhancement after stretch.

biophysics↗

bioRxiv2021

Titin switches from an extensible spring to a mechanical rectifier upon muscle activation

In contracting striated muscle titin acts as a spring in parallel with the array of myosin motors in each half-sarcomere and could prevent the intrinsic instability of thousands of serially linked half-sarcomeres, if its stiffness, at physiological sarcomere lengths (SL), were ten times larger than reported. Here we define titin mechanical properties during tetanic stimulation of single fibres of frog muscle by suppressing myosin motor responses with Para-Nitro-Blebbistatin, which is able to freeze thick filament in the resting state. We discover that thin filament activation switches I-band titin spring from the large SL-dependent extensibility of the OFF-state to an ON-state in which titin acts as a SL-independent mechanical rectifier, allowing free shortening while opposing stretch with an effective stiffness 4 pN nm-1 per half-thick filament. In this way during contraction titin limits weak half-sarcomere elongation to a few % and, also, provides an efficient link for mechanosensing-based thick filament activation.

physiology↗