Related Experiment Video
Updated: Jul 13, 2026

Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers
Published on: May 4, 2022
The structural coupling between ATPase activation and recovery stroke in the myosin II motor
Sampath Koppole1, Jeremy C Smith, Stefan Fischer
1Computational Biochemistry, Interdisciplinary Center for Scientific Computing (IWR), University of Heidelberg, 69120, Heidelberg, Germany.
Abstract:
Before the myosin motor head can perform the next power stroke, it undergoes a large conformational transition in which the converter domain, bearing the lever arm, rotates approximately 65 degrees . Simultaneous with this "recovery stroke," myosin activates its ATPase function by closing the Switch-2 loop over the bound ATP. This coupling between the motions of the converter domain and of the 40 A-distant Switch-2 loop is essential to avoid unproductive ATP hydrolysis. The coupling mechanism is determined here by finding a series of optimized intermediates between crystallographic end structures of the recovery stroke (Dictyostelium discoideum), yielding movies of the transition at atomic detail. The successive formation of two hydrogen bonds by the Switch-2 loop is correlated with the successive see-saw motions of the relay and SH1 helices that hold the converter domain. SH1 helix and Switch-2 loop communicate via a highly conserved loop that wedges against the SH1-helix upon Switch-2 closing.
Related Concept Videos
ATP Synthase: Structure
ATP Synthase: Mechanism
Excitation-Contraction Coupling in Skeletal Muscles
When an action potential...
Cross-bridge Cycle
ATP Driven Pumps II: P-type Pumps
A typical P-type pump has three cytosolic domains: nucleotide-binding (N), phosphorylation (P), and activator (A) domains. These domains are connected to the membrane-spanning helices by short amino acid segments. ATP hydrolysis and covalent phosphoenzyme intermediate formation are crucial parts of the catalytic cycle. At the highly...
Actin and Myosin in Muscle Contraction

