Kinetic differences at the single molecule level account for the functional diversity of rabbit cardiac myosin isoforms

Palmiter, Kimberly A.; Tyska, Matthew J.; Dupuis, D. E.; Alpert, Norman R.; Warshaw, David M.

doi:10.1111/j.1469-7793.1999.0669n.x

Cited by 122 publications

(137 citation statements)

References 46 publications

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“…This is consistent with kinetic measurements in solution [Siemankowski et al, 1985] as well as in vitro mechanical studies suggesting that high ADP concentrations can inhibit actin filament sliding velocities [Homsher et al, 1992;Warshaw et al, 1991;Yamashita et al, 1994]. Using this simple kinetic model to estimate the rate constants for ADP release and ATP binding, Palmiter et al [1999] measured on over a range of ATP concentrations for the V 1 and V 3 cardiac myosin isoforms. k ϩATP for these myosins were similar at ϳ5.5 ϫ 10 6 M Ϫ1 s…”

Section: Determinants Of the Strongly Bound Duration Biochemical Transupporting

confidence: 65%

The myosin power stroke

Tyska

Warshaw

2002

Cell Motil. Cytoskeleton

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181

190

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Optical trapping technology now allows investigators in the motility field to measure the forces generated by single motor molecules. A handful of research groups have exploited this approach to further develop our understanding of the actin-based motor, myosin, an ATPase that is capable of converting chemical energy into mechanical work during a cyclical interaction with filamentous actin. In this regard, myosin-II from muscle is the most well-characterized myosin superfamily member. By combining the data obtained from optical trap assays with that from ensemble biochemical and mechanical assays, this review discusses the fundamental properties of the myosin-II power stroke and, perhaps more significantly, how these properties are governed by this molecule's atomic structure and the biochemical transitions that define its catalytic cycle. Cell Motil. Cytoskeleton 51:1-15, 2002.

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Section: Determinants Of the Strongly Bound Duration Biochemical Transupporting

confidence: 65%

The myosin power stroke

Tyska

Warshaw

2002

Cell Motil. Cytoskeleton

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181

190

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“…This finding has important implications for myosin force production and ATP utilization as sarcomere length changes throughout a contraction. Slower MgADP release at longer sarcomere length also provides supporting evidence for a strain-dependent MgADP release mechanism in slow-twitch skeletal fibers, consistent with single-molecule optical trap measurements describing this mechanism in multiple muscle myosin isoforms (31)(32)(33)(34).…”

Section: Discussionsupporting

confidence: 52%

“…Thus, it is likely that these structural alterations to the myofilaments also influence load-dependent mechanisms of MgADP release to slow cross-bridge detachment. Further studies have suggested that release of MgADP requires additional movement of the myosin head after the power stroke to induce a conformational change in the nucleotide binding pocket, freeing MgADP (31)(32)(33)(34)36,62). This ''double step'' was observed in both slow and fast skeletal myosins, and was associated with MgADP release from myosin, in single-molecule optical trap experiments (31).…”

Section: Discussionmentioning

confidence: 99%

Myosin MgADP Release Rate Decreases as Sarcomere Length Increases in Skinned Rat Soleus Muscle Fibers

Fenwick

Leighton

Tanner

2016

Biophysical Journal

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Actin-myosin cross-bridges use chemical energy from MgATP hydrolysis to generate force and shortening in striated muscle. Previous studies show that increases in sarcomere length can reduce thick-to-thin filament spacing in skinned muscle fibers, thereby increasing force production at longer sarcomere lengths. However, it is unclear how changes in sarcomere length and lattice spacing affect cross-bridge kinetics at fundamental steps of the cross-bridge cycle, such as the MgADP release rate. We hypothesize that decreased lattice spacing, achieved through increased sarcomere length or osmotic compression of the fiber via dextran T-500, could slow MgADP release rate and increase cross-bridge attachment duration. To test this, we measured cross-bridge cycling and MgADP release rates in skinned soleus fibers using stochastic length-perturbation analysis at 2.5 and 2.0 mm sarcomere lengths as pCa and [MgATP] varied. In the absence of dextran, the force-pCa relationship showed greater Ca 2þ sensitivity for 2.5 vs. 2.0 mm sarcomere length fibers (pCa 50 ¼ 5.68 5 0.01 vs. 5.60 5 0.01). When fibers were compressed with 4% dextran, the length-dependent increase in Ca 2þ sensitivity of force was attenuated, though the Ca 2þ sensitivity of the force-pCa relationship at both sarcomere lengths was greater with osmotic compression via 4% dextran compared to no osmotic compression. Without dextran, the cross-bridge detachment rate slowed by~15% as sarcomere length increased, due to a slower MgADP release rate (11.2 5 0.5 vs. 13.5 5 0.7 s À1 ). In the presence of dextran, cross-bridge detachment was~20% slower at 2.5 vs. 2.0 mm sarcomere length due to a slower MgADP release rate (10.1 5 0.6 vs. 12.9 5 0.5 s À1 ). However, osmotic compression of fibers at either 2.5 or 2.0 mm sarcomere length produced only slight (and statistically insignificant) slowing in the rate of MgADP release. These data suggest that skeletal muscle exhibits sarcomere-length-dependent changes in cross-bridge kinetics and MgADP release that are separate from, or complementary to, changes in lattice spacing.

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“…Inherent in this analysis is the idea that V actin is a detachment-limited process (16), where V actin is proportional to myosin's unitary step size (d) divided by the duration of actin strong binding (t on ), i.e., V actin Ϸ d/t on . In this model, the duration of strong actin binding can be further dissected into the time required for ADP release by myosin, plus the time required for ATP to bind and cause dissociation from actin (rigor time) (24). Assuming a value for d of 10 nm (10), we constructed a double reciprocal plot to derive the rate constants for ADP release (k ϪADP ) and the second-order k ϩATP constants under each condition (Fig.…”

Section: Kinetic Analysismentioning

confidence: 99%

Phosphate enhances myosin-powered actin filament velocity under acidic conditions in a motility assay

Debold

Turner

Stout

et al. 2011

American Journal of Physiology-Regulatory, Integrative and Comp

102

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Debold EP, Turner MA, Stout JC, Walcott S. Phosphate enhances myosin-powered actin filament velocity under acidic conditions in a motility assay. Am J Physiol Regul Integr Comp Physiol 300: R1401-R1408, 2011. First published February 23, 2011 doi:10.1152/ajpregu.00772.2010.-Elevated levels of inorganic phosphate (Pi) are believed to inhibit muscular force by reversing myosin's force-generating step. These same levels of Pi can also affect muscle velocity, but the molecular basis underlying these effects remains unclear. We directly examined the effect of Pi (30 mM) on skeletal muscle myosin's ability to translocate actin (Vactin) in an in vitro motility assay. Manipulation of the pH enabled us to probe rebinding of Pi to myosin's ADP-bound state, while changing the ATP concentration probed rebinding to the rigor state. Surprisingly, the addition of Pi significantly increased Vactin at both pH 6.8 and 6.5, causing a doubling of Vactin at pH 6.5. To probe the mechanisms underlying this increase in speed, we repeated these experiments while varying the ATP concentration. At pH 7.4, the effects of Pi were highly ATP dependent, with Pi slowing Vactin at low ATP (Ͻ500 M), but with a minor increase at 2 mM ATP. The Pi-induced slowing of Vactin, evident at low ATP (pH 7.4), was minimized at pH 6.8 and completely reversed at pH 6.5. These data were accurately fit with a simple detachment-limited kinetic model of motility that incorporated a Pi-induced prolongation of the rigor state, which accounted for the slowing of Vactin at low ATP, and a Pi-induced detachment from a strongly bound post-power-stroke state, which accounted for the increase in Vactin at high ATP. These findings suggest that Pi differentially affects myosin function: enhancing velocity, if it rebinds to the ADP-bound state, while slowing velocity, if it binds to the rigor state.fatigue; cross-bridge cycle; muscle contraction MUSCULAR FORCE AND MOTION are generated through the cyclical interaction of actin and myosin, in a process ultimately powered by the hydrolysis of ATP (Fig. 1). In the 1980s, several investigations established that elevated levels of organic phosphate (P i ) reduced muscular force, leading to the notion that P i release by myosin was closely associated with force generation (12) and the rotation of the lever arm (2). This hypothesis postulates that P i rebinds to myosin (M) in a state in which myosin is strongly bound to both actin (A) and ADP (AM.ADP) and, in one or more steps, reverses the forcegenerating step, leading to an increase in the population of the weakly bound myosin, in the M.ADP.P i state (32). While competing theories exist (3), models based on the P i -induced detachment can account for much of the effect on muscular force (26). However, the effects of P i on muscle's shortening velocity have been more difficult to explain using the same model.While the earliest experiments in muscle fibers suggested that P i had no effect on unloaded shortening velocity (V us ) (7), subsequent efforts revealed that P i could induc...

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Kinetic differences at the single molecule level account for the functional diversity of rabbit cardiac myosin isoforms

Cited by 122 publications

References 46 publications

The myosin power stroke

The myosin power stroke

Myosin MgADP Release Rate Decreases as Sarcomere Length Increases in Skinned Rat Soleus Muscle Fibers

Phosphate enhances myosin-powered actin filament velocity under acidic conditions in a motility assay

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