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The Power Stroke

“Cocked” The ATP pocket closes and the myosin head again changes shape which causes it to move 5nm further down the actin filament ATP hydrolysis occurs, but the products – ADP and Pi – remain tightly bound in the pocket. “Attached” ADP is released during the power stroke

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The Power Stroke

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  1. “Cocked” • The ATP pocket closes and the myosin head again changes shape which causes it to move 5nm further down the actin filament • ATP hydrolysis occurs, but the products – ADP and Pi – remain tightly bound in the pocket “Attached” • ADP is released during the power stroke • Myosin is attached in the rigor complex, the ATP pocket is open and waiting for a new cycle to begin The Power Stroke ATP ADP Pi ADP Pi “Force-Generating” • Myosin reattaches to actin (5nm further down the filament than the original site) • Initially, this binding is weak, but the release of Pi causes a conformational change in the head which: • Strengthens the attachment of myosin • Initiates the power stroke Ca “Released” • ATP enters the pocket on the back of the myosin head • This leads to a decrease in the binding affinity for actin, and the myosin head detaches “Attached” • without any energy, the myosin remains attached very tightly to actin • this is the rigor complex and is short lived

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