Effect of actin concentration on the intermediate oxygen exchange of myosin; relation to the refractory state and the mechanism of exchange

Sleep, John; Boyer, Paul D.

doi:10.1021/bi00618a015

Cited by 36 publications

(7 citation statements)

References 26 publications

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“…to account for the low degree of association of heavy meromyosin or subfragment 1 with actin observed under conditions approaching the maximum velocity at low temperature, Eisenberg and coworkers [37 -391 proposed that a transition from a hypothetical refractory state of the myosin-product complex, unable to bind to actin, to a nonrefractory one being in a rapid equilibrium with actin is the rate-limiting step. However, the refractory state model is not consistent with the recent results of Sleep and Boyer [40] concerning the effect of actin concentration on the myosincatalysed exchange of phosphate oxygens with water during ATP hydrolysis. Moreover, at 20°C a good correlation between the proportion of subfragment-I bound to actin and the percentage saturation of the acto-subfragment-1 ATPase has recently been found [41].…”

Section: Discussioncontrasting

confidence: 92%

Chicken‐Gizzard Actin

Próchniewicz

Strzelecka‐Gołaszewska

1980

European Journal of Biochemistry

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Interaction of actin from chicken gizzard and from rabbit skeletal muscle with rabbit skeletal muscle myosin was compared by measuring the rate of superprecipitation, the activation of the Mg‐ATPase and inhibition of K‐ATPase activity of myosin and heavy meromyosin, and determination of binding of heavy meromyosin in the absence of ATP. Both the rate of superprecipitation of the hybrid actomyosin and the activation of myosin ATPase by gizzard actin are lower than those obtained with skeletal muscle actin. The activation of myosin Mg‐ATPase by the two actin species also shows different dependence on substrate concentration: with gizzard actin the substrate inhibition starts at lower ATP concentration. The double‐reciprocal plots of the Mg‐ATPase activity of heavy meromyosin versus actin concentration yield the same value of the extrapolated ATPase activity at infinite actin concentration (V) for the two actins and nearly double the actin concentration needed to produce half‐maximal activation (Kapp) in the case of gizzard actin. A corresponding difference in the abilities of the two actin species to inhibit the K‐ATPase activity of heavy meromyosin in the absence of divalent cations was also observed. The results are discussed in terms of the effect of substitutions in the amino acid sequence of gizzard and skeletal muscle actins on their interaction with myosin.

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Section: Discussioncontrasting

confidence: 92%

Chicken‐Gizzard Actin

Próchniewicz

Strzelecka‐Gołaszewska

1980

European Journal of Biochemistry

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“…After several cycles, ATP undergoes almost complete oxygen exchange with the solvent. This oxygen exchange is also observed in the presence of actin (49) but at a slower rate (55,56), because instead of favoring phosphate rotation, the acto-myosin complex induces product release. The rates and equilibrium constants of the forward and reverse ATP hydrolysis reaction in Dictyostelium myosin II at varying temperatures have been reported (57).…”

Section: Discussionmentioning

confidence: 69%

Stabilization of the ADP/Metaphosphate Intermediate during ATP Hydrolysis in Pre-power Stroke Myosin

Kiani

Fischer

2013

Journal of Biological Chemistry

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Background: It is unknown how enzymes actually achieve the catalytic pathways proposed for ATP hydrolysis. Results: A quantum mechanical analysis of myosin ATPase quantifies the relevant interactions that stabilize a metaphosphate intermediate. Conclusion:The protein is designed to stabilize this metaphosphate, key to the enzymatic mechanism. Significance: This yields a chemically consistent model for the catalytic strategy of nucleotide-hydrolyzing enzymes in general.

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“…Although the exchange is markedly reduced with tethered acto-HMM, there is still significant exchange. With acto-Si at high ATP, in contrast, there is little or no residual exchange at saturating actin (20 (28). At high ATP, this ATP release does not inhibit the overall rate as ATP rebinding will be fast, but at low ATP levels, rebinding will be slow and the net rate will be reduced.…”

Section: Discussionmentioning

confidence: 98%

Catalytic consequences of oligomeric organization: kinetic evidence for "tethered" acto-heavy meromyosin at low ATP concentrations.

Hackney¹,

Clark²

1984

Proc. Natl. Acad. Sci. U.S.A.

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The influence of the supramolecular organization of myosin on its ATPase activity was investigated at a range of ATP concentrations, using as a model system subfragment 1 (Si) and heavy meromyosin (HMM), which are respectively monomeric and dimeric proteolytic fragments of myosin. At low ATP levels in the presence of a molar excess of actin, dimeric HMM showed an increased rate of ATP hydrolysis relative to that for monomeric S1. This increased ATPase for HMM was inhibited by high concentrations of ATP, which reduced the acto-HMM ATPase rate to the lower level of acto-S1. This observation is consistent with the rapid ATP hydrolysis of acto-HMM at low ATP being due to rapid product release from a "tethered" acto-HMM species, which has product bound to one head group while the other head group remains bound to actin. At high concentrations of ATP, ATP binds to both head groups, resulting in net dissociation of HMM from actin. This model is supported by 180 exchange data. Acto-HMM hydrolyzed ATP with extensive exchange of water oxygens into Pi at high ATP levels, but not at low ATP levels.Acto-Sl exhibited extensive exchange at both high and low ATP levels. This result is consistent with rapid product release from a tethered acto-HMM intermediate at low ATP.The possible catalytic significance of the organization of enzymes into supramolecular structures is a problem that is central to the extension of enzymology from the study of reactions in dilute solution in vitro into the complexity of reactions as they occur in vivo. The proteins responsible for movement are an excellent model system for investigating such effects. In this case, the supramolecular organization is an integral component for the production of force, and thus supramolecular organization and catalysis are very closely intertwined. Additionally, the state of organization can often be manipulated experimentally so that the enzymatic properties can be determined at a range of different organizational states. This is particularly true for nonmuscle motile systems in which the structures must be capable of dynamic rearrangements such as in amoeboid movement, but it is also true of muscle, in which limited proteolysis can produce active fragments and intermediate states such as myosin minifilaments can be formed (1).Myosin is a dimeric enzyme that catalyzes the hydrolysis of ATP and uses the free energy released by this hydrolysis to drive the mechanical contraction of muscle in conjunction with actin, the other major muscle protein (see refs. 2-5 for review). The myosin molecule is asymmetric with a long "coiled coil" tail composed of one a-helix from each monomeric unit. At the end of each helix is a globular head group, which contains the sites for ATP hydrolysis and actin binding. At physiological ionic strength, myosin molecules aggregate into filaments through alignment of their tail regions. The globular head groups project away from the filament, where they can interact with actin filaments. Limited proteolysis can cleave myosin at the ne...

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Effect of actin concentration on the intermediate oxygen exchange of myosin; relation to the refractory state and the mechanism of exchange

Cited by 36 publications

References 26 publications

Chicken‐Gizzard Actin

Chicken‐Gizzard Actin

Stabilization of the ADP/Metaphosphate Intermediate during ATP Hydrolysis in Pre-power Stroke Myosin

Catalytic consequences of oligomeric organization: kinetic evidence for "tethered" acto-heavy meromyosin at low ATP concentrations.

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