Kinetics of Nucleoside Triphosphate Cleavage and Phosphate Release Steps by Associated Rabbit Skeletal Actomyosin, Measured Using a Novel Fluorescent Probe for Phosphate

White, Howard D.; Belknap, Betty; Webb, Martin R.

doi:10.1021/bi970540h

Cited by 176 publications

(246 citation statements)

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“…DOUBTS ABOUT SCHEME 1 Development of a sensitive chromophoric probe of P i release allowed the rate of release from actomyosin to be measured directly. White et al (1997) found that P i release from actomyosin in solution is only 75 s À1 , not sufficiently faster than the ATP hydrolysis step to support the assumption of a rapid equilibrium described above. More complex schemes could, of course, be invoked, and integration of pressure-and temperature-jump and fibre transient data led Ranatunga (1999) to postulate yet another state in this part of the actomyosin cycle.…”

Section: Details Of the Link Between Phosphatementioning

confidence: 70%

“…A structural change, such as tilting of the myosin head, accompanying release of the hydrolysis products from AMÁADPÁP i , causes the thick and thin filaments to slide. The order of dissociation from MÁADPÁP i is first orthophosphate (P i ), then ADP (Trentham et al 1972), and the same order applies to product release from AMÁADPÁP i in solution (White et al 1997) and in muscle fibres (Dantzig & Goldman 1985). In solution experiments with the isolated proteins, the product release steps liberate more than half of the free energy available from the net ATPase reaction, and most of this free energy change corresponds to P i release (White & Taylor 1976;Siemankowski et al 1985).…”

Section: Hints From Biochemistrymentioning

confidence: 99%

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Coupling between phosphate release and force generation in muscle actomyosin

Takagi

Shuman

Goldman

2004

Phil. Trans. R. Soc. Lond. B

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Energetic, kinetic and oxygen exchange experiments in the mid-1980s and early 1990s suggested that phosphate (P i ) release from actomyosin-adenosine diphosphate P i (AMÁADPÁP i ) in muscle fibres is linked to force generation and that P i release is reversible. The transition leading to the force-generating state and subsequent P i release were hypothesized to be separate, but closely linked steps. P i shortens single force-generating actomyosin interactions in an isometric optical clamp only if the conditions enable them to last 20-40 ms, enough time for P i to dissociate. Until 2003, the available crystal forms of myosin suggested a rigid coupling between movement of switch II and tilting of the lever arm to generate force, but they did not explain the reciprocal affinity myosin has for actin and nucleotides. Newer crystal forms and other structural data suggest that closing of the actin-binding cleft opens switch I (presumably decreasing nucleotide affinity). These data are all consistent with the order of events suggested before: myosinÁADPÁP i binds weakly, then strongly to actin, generating force. Then P i dissociates, possibly further increasing force or sliding.

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Section: Details Of the Link Between Phosphatementioning

confidence: 70%

Section: Hints From Biochemistrymentioning

confidence: 99%

Coupling between phosphate release and force generation in muscle actomyosin

Takagi

Shuman

Goldman

2004

Phil. Trans. R. Soc. Lond. B

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“…For example, phosphate release from activated Acanthamoeba myosin-Ic = 24 s -1 (26), myosin-V > 100 s -1 (22,33), and skeletal muscle myosin-II = 75 s -1 (24). It is not clear why myo1b evolved to have a slow rate of phosphate release, but it is likely that the motor is kinetically tuned to optimally sense tension allowing for force-dependent changes in its duty ratio (see below).…”

Section: Phosphate Releasementioning

confidence: 99%

“…This mantATP-induced dissociation is ∼ 2-fold slower than ATP-induced dissociation as measured by pyrene-actin fluorescence (1.5 ± 0.081 μM -1 s -1 ; Table 1). Fluorescently-labeled phosphate-binding protein (P i BP) was used to measure directly the rate of phosphate release (k +4 ′) in sequential-mix, single-turnover, stopped-flow experiments (11,22,24,26). Myo1b IQ was mixed with ATP, aged 7 s to allow for ATP binding and hydrolysis, and mixed with actin ( Figure 6).…”

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confidence: 99%

Temperature Dependence of Nucleotide Association and Kinetic Characterization of Myo1b

et al. 2006

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Myo1b is a widely expressed myosin-I isoform that concentrates on endosomal and ruffling membranes and is thought to play roles in membrane trafficking and dynamics. It is one of the best characterized myosin-I isoforms and appears to have unique biochemical properties tuned for tension sensing or tension maintenance. We determined the key biochemical rate constants that define the actomyo1b ATPase cycle at 37 °C and measured the temperature dependence of ATP binding, ADP release, and the transition from a nucleotide inaccessible state to a nucleotide accessible state (kalpha). The rate of ATP binding is highly temperature sensitive, with an Arrhenius activation energy 2-3 fold greater than other characterized myosins (e.g, myosin-II and myosin-V). ATP hydrolysis is fast, and phosphate release is slow and rate limiting with an actin dependence that is nearly identical to the steady-state ATPase parameters (V max and K ATPase ). ADP release is not as temperature dependent as ATP binding. The rates and temperature dependence of ADP release are similar to kalpha suggesting a similar structural change is responsible for both transitions. We calculate a duty ratio of 0.08 based on the biochemical kinetics. However, this duty ratio is likely to be highly sensitive to strain.Myosin-Is are the single-headed, low-molecular-weight members of the myosin superfamily that are proposed to link cellular membranes with the actin cytoskeleton. Myosin-I isoforms bind phosphoinositides directly (1) and function in several important cellular processes, including membrane retraction, macropinocytosis, phagocytosis, membrane trafficking, cellcell adhesion, and mechanical signal transduction (2-8).The biochemical mechanisms of long-tail and short-tail myosin-I isoforms have been studied (9-12), with myo1b being the best characterized short-tail isoform (13)(14)(15). The myo1b ATPase mechanism (Scheme 1) is notable in that (a) the maximum rate of ATP binding and population of the myo1b IQ weakly-bound states is > 30-fold slower than myosin-II, (b) nucleotide-free myo1b is in equilibrium between a state that binds nucleotide (AM′) and a state that does not bind nucleotide (AM), (c) the rate of transition between AM and AM′ (k +α ) states is similar to the rate of ADP release (k +5 ′), and (d) ADP release is slow and is accompanied by a rotation of the lever arm.We proposed that the strikingly slow actomyo1b ATPase rate constants are a property of all short-tail myosin-I isoforms (11,16). However, it has been shown recently that short-tailed Dictyostelium myosin-IE (not to be confused with vertebrate long-tail myo1e (11)) has kinetic rate constants that are substantially faster than vertebrate short-tail isoforms (12). Because of † EMO was supported by grants from the National Institutes of Health (GM57247 and AR051174). JHL was supported by a training grant from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (AR053461). *Corresponding author: E. Michael Ostap, Department of Physiology, University of Pe...

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“…The first-order rate of actin dissociation from AM⅐T at 25°C is Ͼ5,000 s Ϫ1 (7), which is probably significantly faster than the competing repriming step (AMo⅐T 3 AMc⅐T). The latter rate has not been measured but the rate of the equivalent step in the absence of actin is Ϸ300 s Ϫ1 (23,25) and the overall rate of the composite hydrolysis step (i.e., open to closed and hydrolysis itself) is slowed by the binding of actin (26,27). The rate (AMo⅐T 3 AMc⅐T) is probably no more than 300 s Ϫ1 , which would lead to the pathway of dissociation before repriming being greatly favored.…”

Section: Discussionmentioning

confidence: 99%

Repriming the actomyosin crossbridge cycle

Walter

Sleep

2004

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

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The central features of the mechanical cycle that drives the contraction of muscle are two translational steps: the working stroke, whereby an attached myosin crossbridge moves relative to the actin filament, and the repriming step, in which the crossbridge returns to its original orientation. Although the mechanism of the first of these is understood in some detail, that of the second has received less attention. Here, we show that repriming occurs after detachment of the crossbridge from the actin, rather than intervening between two actomyosin states with ATP bound [Eisenberg, E. & Greene, L. E. (1980) Annu. Rev. Physiol. 42, 293-309]. To discriminate between these two models we investigated the single-molecule mechanics of the myosin-actin interaction in the presence of ATP analogues such as GTP, for which the hydrolytic step itself limits the actomyosin GTPase rate to a much lower rate than for ATP. The lifetimes of bound states was proportional to 1͞ [GTP], indicating that during the bound period myosin was in the actomyosin rigor configuration. Moreover, despite the very low actomyosin GTPase, the rate of actin binding and formation of the rigor state was higher than with ATP; it follows that most interactions with actin result in the release of GTP and not of the products, GDP and phosphate. There was no significant movement of the actin during this interaction, so repriming must occur while myosin is dissociated, as in the original Lymn- Taylor T he mechanical events responsible for muscle contraction are coupled to the actomyosin ATPase cycle. According to the basic scheme of Lymn and Taylor (L-T) (1) (Fig. 1A), in the relaxed state (crossbridge 90°to the filament axes) the myosin (M) is bound to ADP (D) and phosphate (P). The binding of actin (A) to M⅐D⅐P 90 leads to the working stroke, accompanied by product release and the formation of the rigor AM 45 state. ATP (T) binds to AM to form AM⅐T, from which actin rapidly dissociates. Hydrolysis then takes place while myosin is dissociated from actin, and the mechanical repriming of the crossbridge, which positions it for the start of the next cycle, is associated with this step. Further research by Eisenberg and collaborators (2) added important details to the scheme. The concentration of Ca 2ϩ regulates the binding to actin of the so-called ''strong binding'' set of myosin states (M and M⅐D) but has little effect on the binding of the ''weak'' states (M⅐T and M⅐D⅐P). This finding suggested that these two sets of states bind to actin in different conformations (2), from which it was natural to infer that the transition between these conformations might correspond to the working stroke. Moreover, the free energy change between M⅐T and M⅐D⅐P was very small (3), and the two complexes bound to actin with similar affinities (4), at least 2 orders of magnitude weaker than that of the strong states. The actin association constant appeared to be a marker for the inferred two conformational states. In this case, as argued by Eisenberg and Greene (5), the logical...

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Kinetics of Nucleoside Triphosphate Cleavage and Phosphate Release Steps by Associated Rabbit Skeletal Actomyosin, Measured Using a Novel Fluorescent Probe for Phosphate

Cited by 176 publications

References 34 publications

Coupling between phosphate release and force generation in muscle actomyosin

Coupling between phosphate release and force generation in muscle actomyosin

Temperature Dependence of Nucleotide Association and Kinetic Characterization of Myo1b

Repriming the actomyosin crossbridge cycle

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