Key result
Single-molecule optical tweezers assay revealed that a single interaction of α-actinin and titin is weak under applied force, but unbinding forces can more than triple depending on force direction.
Multiple α-actinin/Z-repeat interactions likely cooperate to ensure long-term stable titin anchoring in the muscle Z-disk while allowing dynamic exchange of individual components.
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Directional force sensitivity may stabilize cardiac Z-disks; leaves open relevance to human cardiomyopathy.
Stable anchoring of titin within the muscle Z-disk is essential for preserving muscle integrity during passive stretching. One of the main candidates for anchoring titin in the Z-disk is the actin cross-linker α-actinin. The calmodulin-like domain of α-actinin binds to the Z-repeats of titin. However, the mechanical and kinetic properties of this important interaction are still unknown. Here, we use a dual-beam optical tweezers assay to study the mechanics of this interaction at the single-molecule level. A single interaction of α-actinin and titin turns out to be surprisingly weak if force is applied. Depending on the direction of force application, the unbinding forces can more than triple. Our results suggest a model where multiple α-actinin/Z-repeat interactions cooperate to ensure long-term stable titin anchoring while allowing the individual components to exchange dynamically.
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Grison et al. (2017) studied this question. Dual-beam optical tweezers assay was evaluated on Mechanical and kinetic properties of α-actinin and titin interaction. Single-molecule optical tweezers assay revealed that a single interaction of α-actinin and titin is weak under applied force, but unbinding forces can more than triple depending on force direction.
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