What question did this study set out to answer?

To determine how calcium ions regulate the dissociation kinetics of 1-N6-ethenoadenosine diphosphate from rabbit skeletal muscle actomyosin subfragment 1.

July 1, 1987Journal of Biological ChemistryOpen Access

The dissociation of 1-N6-ethenoadenosine diphosphate from regulated actomyosin subfragment 1.

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Why the study?

Does the absence of calcium ion affect the dissociation rate of epsilon ADP from regulated actomyosin subfragment 1 in rabbit skeletal muscle?

Key Points

To determine how calcium ions regulate the dissociation kinetics of 1-N6-ethenoadenosine diphosphate from rabbit skeletal muscle actomyosin subfragment 1.
Measured the decay of fluorescence emission upon dissociation of bound 1-N6-ethenoadenosine diphosphate (epsilon ADP) from regulated rabbit skeletal actomyosin subfragment 1 in the presence and absence of calcium ions.
Fitted fluorescence changes to a multi-exponential kinetic scheme featuring two first-order transition intermediates prior to ligand release.
The effective dissociation rate of epsilon ADP from the actomyosin subfragment 1 complex was approximately 10- to 15-fold lower in the absence of calcium ion than in its presence.
Both forward rate constants (k-1 and k-2) preceding the dissociation step showed an approximate 15-fold reduction without calcium.
Calcium removal similarly decreased dissociation rate constants across epsilon ATP, epsilon ADP-Pi, and epsilon ADP, demonstrating that calcium regulation primarily targets transition states between actomyosin-nucleoside complexes.

Structured PICO

Does the absence of calcium ion affect the dissociation rate of epsilon ADP from regulated actomyosin subfragment 1 in rabbit skeletal muscle?

Population

Rabbit skeletal muscle (regulated actin X subfragment 1 X epsilon ADP complex)

Intervention

Absence of calcium ion

Comparator

Presence of calcium ion

Outcome

Effective rate of dissociation of 1-N6-ethenoadenosine diphosphate (epsilon ADP)surrogate

The primary effect in calcium regulation of the actin-subfragment 1 ATPase is on the rate constant of transitions between actomyosin-nucleoside phosphate complexes.

Discussion

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Implication

May inform molecular models of actomyosin regulation; leaves open translation to human cardiac muscle.

Cite This Study

Rosenfeld et al. (1987) studied this question.

synapsesocial.com/papers/6a76faade29fd788c9f6f7fb https://doi.org/10.1016/s0021-9258(18)61064-6

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The dissociation of 1-N6-ethenoadenosine diphosphate from regulated actomyosin subfragment 1.

Key Points

Structured PICO

Discussion

Implication

Cite This Study

The dissociation of 1-N6-ethenoadenosine diphosphate from regulated actomyosin subfragment 1.

Key Points

Structured PICO

Discussion

Implication

Cite This Study

Also Consider

Also Consider