The phosphorylation-dephosphorylation process as a myosin-linked regulation of superprecipitation of fast skeletal muscle actomyosin

Kakol, I; Kasman, Krystyna; Michnicka, Malgorzata

doi:10.1016/0167-4838(82)90065-6

Cited by 17 publications

(3 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Results concerning an effect of phosphorylation upon myosin ATPase activity vary widely. Myosin ATPase activity has been reported to decrease (Cooke et al, 1982;Kakol et al, 1982) remain unchanged (Morgan et al, 1976;Persichini and Stull, 1984) and to increase (Pemrick, 1980) after LC~ phosphorylation, although most of these measurements were made in the absence of the thin filament regulatory proteins and thus may not be applicable to intact muscles. Perhaps most relevant to this discussion is the finding that the concentration of calcium for half-maximal activation (i.e., pCas0)) of myosin ATPase activity in the presence of regulated actin was unchanged after phosphorylation (Pemrick, 1980).…”

Section: P04mentioning

confidence: 99%

Variations in cross-bridge attachment rate and tension with phosphorylation of myosin in mammalian skinned skeletal muscle fibers. Implications for twitch potentiation in intact muscle.

Metzger

Greaser

Moss

1989

The Journal of General Physiology

272

245

View full text Add to dashboard Cite

The Ca 2+ sensitivities of the rate constant of tension redevelopment (ktr; Brenner, B., and E. Eisenberg. 1986. Proceedings of the National Academy of Sciences. 83: 3542-3546) and isometric force during steady-state activation were examined as functions of myosin light chain 2 (LC~) phosphorylation in skinned single fibers from rabbit and rat fast-twitch skeletal muscles. To measure ktr the fiber was activated with Ca 2+ and steady isometric tension was allowed to develop; subsequently, the fiber was rapidly (< 1 ms) released to a shorter length and then reextended by ~200 nm per half sarcomere. This maneuver resulted in the complete dissociation of cross-bridges from actin, so that the subsequent redevelopment of tension was related to the rate of cross-bridge reattachment. The time course of tension redevelopment, which was recorded under sarcomere length control, was best fit by a first-order exponential equation (i.e., tension = C(1 -e -~) to obtain the value of kt~. In control fibers, ktr increased sigmoidally with increases in [Ca 2+] ; maximum values of ktr were obtained at pCa 4.5 and were significantly greater in rat superficial vastus lateralis fibers (26.1 + 1.2 s-1 at 15~ than in rabbit psoas fibers (18.7 _+ 1.0 s-l). Phosphorylation of LC~ was accomplished by repeated Ca 2+ activations (pCa 4.5) of the fibers in solutions containing 6 #M calmodulin and 0.5/~M myosin light chain kinase, a protocol that resulted in an increase in LC~ phosphorylation from ~ 10% in the control fibers to >80% after treatment. After phosphorylation, kt~ was unchanged at maximum or very low levels of Ca 2+ activation. However, at intermediate levels of Ca ~ § activation, between pCa 5.5 and 6.2, there was a significant increase in ktr such that this portion of the ktr-pCa relationship was shifted to the left. The steady-state isometric tension-pCa relationship, which in control fibers was left shifted with respect to the ktr-pCa relationship, was further left-shifted after LC~ phosphorylation. Phosphorylation of LC2 had no effect upon steady-state tension during maximum Ca 2+ activation. In fibers from which troponin C was partially extracted to disrupt molecular cooperativity within the thin filament (Moss et al. 1985. Journal of General Physiology.86:585-600), the effect of LC2 phosphorylation to increase the Ca ~+ sensitivity of steady-state isometric force was no longer evident, although the effect of phosphorylation to increase ktr was unaffected by this maneuver. Readdition of purified troponin C to the extracted fibers restored the effect of phosphorylation to potentiate force at submaximal levels of Ca ~+ activation. Thus, the mechanism of phosphorylation-dependent increases in steady-state isometric force appears to involve modulation of the effect of cross-bridges bound to actin to cooperatively enhance the Ca ~+ activation of the thin filament. The observation of a phosphorylationdependent increase in the Ca 2+ sensitivity of k,r likely has important implications in terms of dynamic contractile funct...

show abstract

Section: P04mentioning

confidence: 99%

Variations in cross-bridge attachment rate and tension with phosphorylation of myosin in mammalian skinned skeletal muscle fibers. Implications for twitch potentiation in intact muscle.

Metzger

Greaser

Moss

1989

The Journal of General Physiology

272

245

View full text Add to dashboard Cite

show abstract

“…Further study demonstrates that the ATPase activity of myosin from rabbit fast‐twitch skeletal muscle is not significantly changed by MRLC phosphorylation (Morgan et al ., ). Some other studies report that the actomyosin ATPase activity was higher when the MRLC is in dephosphorylated form when it is determined under conditions similar to physiological (Kakol et al ., ; Michnicka et al ., ), which is in agreement with our result. In our experiment, it showed that the phosphorylation level of MRLC decreased gradually following the incubation time in the control and AP groups, but in the phosphatase inhibitor group, it gradually decreased after a stable period, while the actomyosin ATPase activity presented a slowly decrease after a gradual increase in the three groups.…”

Section: Discussionmentioning

confidence: 99%

Dephosphorylation of myosin regulatory light chain modulates actin–myosin interaction adverse to meat tenderness

Gao

et al. 2017

Int J of Food Sci Tech

View full text Add to dashboard Cite

The objective of this study was to investigate the relationship between the dephosphorylation of myosin regulatory light chain and actin-myosin interaction after muscle homogenate was treated with alkaline phosphatase and phosphatase inhibitor. The myosin regulatory light chain was significantly dephosphorylated by alkaline phosphatase after incubation. Among different groups, dephosphorylated myosin regulatory light chain to a much greater extent leads to a lower actomyosin dissociation degree, thereby raising the actomyosin ATPase activity, whereas it exhibits a higher actomyosin dissociation degree and a lower actomyosin ATPase activity when the myosin regulatory light chain was in a low dephosphorylated state. The data suggest that the dephosphorylation of myosin regulatory light chain modulates actomyosin dissociation (the number of myosin interact with actin) negatively and has a positive influence on actomyosin ATPase activity (the interacting force between myosin and actin).Dephosphorylation modulates actinmyosin X. Gao et al.

show abstract

“…With few exceptions [5,7], reports of inhibition following LC2 removal came from studies using low ionic strength, whereas positive effects were observed exclusively at around physiological ionic strength. Similarly, the phosphorylated form of LC2 (LC2-P) has been observed to exert opposite effects at the extremes of ionic strength ( [11] versus [12]). These observations led to the hypothesis that LC2 is involved in binding certain polyanions, such as ATPfree and/or phosphate (as LC2-P), to become an activator or an inhibitor of the actomyosin MgATPase activity, depending upon the experimental conditions [13].…”

Section: Introductionmentioning

confidence: 99%

ATP, uncomplexed by divalent cations, and the LC2 light chain are interdependent modifiers of the skeletal actomyosin MgATPase activity

Pemrick

Martínez

1991

Biochemical Journal

View full text Add to dashboard Cite

In the absence of troponin and tropomyosin, skeletal actomyosin MgATPase activity can be altered by 2-3-fold by divalent cations. The 'sign' of this effect (i.e. inhibition or activation) varies with ionic strength. To investigate the mechanism, P(i) liberation was analysed at both low and high ionic strength with three concentrations of MgATP and over a wide range of Mg2+ concentrations. This procedure separated the effects of two dependent variables, Mg2+ and ATP4-/3- (ATPfree), to provide the following observations. (1) ATPfree, not Mg2+ (nor Ca2+), was the modifier. (2) ATPfree was an activator at low ionic strength and an inhibitor at high ionic strength, with half-maximal activation/inhibition occurring between 0.75 and 0.8 mM-ATPfree. (3) The rate constants controlling Vmax. with respect to actin were increased up to 3-fold by ATPfree at low ionic strength, and decreased up to 3-fold by ATPfree at high ionic strength. (4) The effect of ATPfree required near-native levels of the LC2 light chain bound to myosin (i.e. 2 mol of LC2/mol of myosin). (5) Sensitivity of P(i) liberation to a 50% decrease in the LC2 content of myosin required high ATPfree concentrations. It is concluded that LC2 and ATPfree are interdependent, non-additive, modifiers of MgATPase. These results are consistent with thin filament regulation of skeletal muscle contraction, and begin to explain why both positive and negative effects on MgATPase have been attributed to LC2.

show abstract

The phosphorylation-dephosphorylation process as a myosin-linked regulation of superprecipitation of fast skeletal muscle actomyosin

Cited by 17 publications

References 21 publications

Variations in cross-bridge attachment rate and tension with phosphorylation of myosin in mammalian skinned skeletal muscle fibers. Implications for twitch potentiation in intact muscle.

Variations in cross-bridge attachment rate and tension with phosphorylation of myosin in mammalian skinned skeletal muscle fibers. Implications for twitch potentiation in intact muscle.

Dephosphorylation of myosin regulatory light chain modulates actin–myosin interaction adverse to meat tenderness

ATP, uncomplexed by divalent cations, and the LC2 light chain are interdependent modifiers of the skeletal actomyosin MgATPase activity

Contact Info

Product

Resources

About