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Schlagwörter:
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Zusammenfassung:
Contraction cycle and inhibitors of actin-L-myosin interaction
1.
1. The term interaction inhibitor describes such substances that never affect L-myosin induced ATP splitting but that, when in the presence of ATP, do inhibit the enzymic interaction between actin and L-myosin, i.e., they convert the Mg-activated actomyosin ATPase reversibly into L-myosin ATPase.
2.
2. Examples of interaction inhibitors are the relaxing factor, discovered by Marsh and Bendall, some polycations, polysulfonates, EDTA, and SCN- in low concentrations.
3.
3. It is shown for polythensulfonate, EDTA, Fuadin, and SCN- and confirmed for the relaxing factor that in the presence of ATP these substances inhibit reversibly the association of actin and L-myosin as well as their chemical interaction.
4.
4. For the fibrils in the water-glycerol extracted fibers this is demonstrated by measuring the resistance to stretching.
5.
5. For gels from natural actomyosin the same conclusion can be drawn, because the actin-component can be almost completely extracted from these gels by an ATP-containing polyethensulfonate solution.
6.
6. Contracted water-glycerol extracted fibers relax as soon as the actin and L-myosin filaments dissociate through the action of ATP and an interaction inhibitor.
7.
7. The dissociation of actin and L-myosin disappears if either the concentration of ATP or that of the interaction inhibitor is sufficiently lowered.
8.
8. In both cases contraction and ATP splitting by Mg-activated actomyosin ATPase occurs anew along with the reappearing association.
9.
9. In the presence of ATP and an interaction inhibitor relaxation even occurs if the Mg-activated actomysin ATPase is converted into the highly effective Ca-activated L-myosin ATPase instead of into the slightly effective Mg-activated L-myosin ATPase.
Hence contraction is only produced when the mechanism of ATP splitting is based on the interaction between actin and L-myosin. Contraction is independent of ATP-splitting by L-myosin ATPase.
