Single-molecule pull-out manipulation of the shaft of the rotary motor F1-ATPase

Tatsuya M. Naito, Tomoko Masaike, Daisuke Nakane, Mitsuhiro Sugawa, Kaoru A. Okada & Takayuki Nishizaka

F1-ATPase is a rotary motor protein in which the central γ-subunit rotates inside the cylinder made of α3β3 subunits. To investigate interactions between the γ shaft and the cylinder at the molecular scale, load was imposed on γ through a polystyrene bead by three-dimensional optical trapping in the direction along which the shaft penetrates the cylinder. Pull-out event was observed under high-load, and thus load-dependency of lifetime of the interaction was estimated. Notably, accumulated counts of lifetime were comprised of fast and slow components. Both components exponentially dropped with imposed loads, suggesting that the binding energy is compensated by the work done by optical trapping. Because the mutant, in which the half of the shaft was deleted, showed only one fast component in the bond lifetime, the slow component is likely due to the native interaction mode held by multiple interfaces.

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