Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display Thick filament Cross-bridge Thin filament Actin binding sites ATP binding sites Tropomyosin Light chains Heavy chains Cross-bridge Troponin Actin Myosin The thick filament called myosin is actually a polymer of myosin molecules, each of which has a flexible cross-bridge that binds atp and actin
The thick filament called myosin is actually a polymer of myosin molecules, each of which has a flexible cross-bridge that binds ATP and actin
The myosin-binding site on actin becomes available, so the The cross-bridge cycle energized cross-bridge binds requires ATP T The full 4.Partial hydrolysis hydrolysis of and departure the bound atP osirid of adp p energizes causes the or“re- cocks flexing of the bridge the bound cross-bridge Binding of a"“ new ATP to the cross-bridge uncouples the bridge
The cross-bridge cycle requires ATP The myosin-binding site on actin becomes available, so the energized cross-bridge binds. 1. The full hydrolysis and departure of ADP + Pi causes the flexing of the bound cross-bridge. 2. Binding of a “new” ATP to the cross-bridge uncouples the bridge. 3. Partial hydrolysis of the bound ATP energizes or “re-cocks” the bridge. 4
The myosin-binding site on actin becomes available, so the energized cross-bridge binds Cross-bridge binds to actin Thin filament(actin, A) [C a- nses Resti Energized ADP ADP muscle cross-bridge Thick filament( myosin, M) M line Z line A+M·ADP·Pl A·M·ADP·Pl
The myosin-binding site on actin becomes available, so the energized cross-bridge binds. 1
ADP A·M·ADP·Pl The full hydrolysis and departure Cross-bridge ADP +P of adp p moves causes the flexing of the bound cross-bridge
The full hydrolysis and departure of ADP + P i causes the flexing of the bound cross -bridge. 2
ATP A+M·ATP Rigor mortis O No ATP ATP binds to myosin (after death) causing cross-bridge Binding of a“ new AtP to the cross-bridge uncouples the bridge
Binding of a “new” ATP to the cross-bridge uncouples the bridge. 3