ADP binding to myosin cross-bridges and its effect on the cross-bridge detachment rate constants.

Schoenberg, Mark J.; Eisenberg, Evan

doi:10.1085/jgp.89.6.905

Cited by 33 publications

(39 citation statements)

References 33 publications

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“…The slope of these plots depended on the MgATP concentration ( Fig. 3 C, inset), consistent with competition between MgADP and MgATP for the same site on myosin (Schoenberg and Eisenberg, 1987). It should be noted that the amplitude of the transient also depended on the addition of creatine kinase when the MgATP concentration was low (Fig.…”

Section: Effects Of Varying Mgadp and Mgatpsupporting

confidence: 75%

Tension transients initiated by photogeneration of MgADP in skinned skeletal muscle fibers.

Lü

Moss

Walker

1993

The Journal of General Physiology

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Addition of MgADP to skinned skeletal muscle fibers causes a rise in Ca2+-activated isometric tension. Mechanisms underlying this tension increase have been investigated by rapid photogeneration of ADP within skinned single fibers of rabbit psoas muscle. Photolysis of caged ADP (PZ-l(2-nitrophenyl)ethyladenosine 5'-diphosphate) resulted in an exponential increase in isometric tension with an apparent rate constant, kADP, of 9.6 --0.3 S -l (mean _+ SE, n--28) and an amplitude, PADP, of 4.9 --+ 0.3% Po under standard conditions (0.5 mM photoreleased MgADP, 4 mM MgATP, pH 7.0, pCa 4.5, 0.18 M ionic strength, 15°C). PADP depended upon the concentration of photoreleased MgADP as well as the concentration of MgATP. A plot of 1/PADP vs. 1/[MgADP] at three MgATP concentrations was consistent with competition between MgADP and MgATP for the same site on the crossbridge. The rate of the transient, kAop, also depended upon the concentration of MgADP and MgATP. At both 4 and 1 mM MgATP, kADP was not significantly different after photorelease of 0.1-0.5 mM MgADP, but was reduced by 28-40% when 3.5 mM MgADP was added before photorelease of 0.5 mM MgADP. kADp was accelerated by about twofold when MgATP was varied from 0.5 to 8 mM MgATP. These effects of MgATP and MgADP were not readily accounted for by population of high force-producing states resulting from reversal of the ADP dissociation process. Rather, the results suggest that competition between MgADP and MgATP for crossbridges at the end of the cycle slows detachment leading to accumulation of force-generating crossbridges. Elevation of steady-state Pi concentration from 0.5 to 30 mM caused acceleration OfkADP from 10.2 _+ 0.5 to 27.8 --1.8 s -1, indicating that the tension rise involved crossbridge flux through the Pi dissociation step of the cycle.

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Section: Effects Of Varying Mgadp and Mgatpsupporting

confidence: 75%

Tension transients initiated by photogeneration of MgADP in skinned skeletal muscle fibers.

Lü

Moss

Walker

1993

The Journal of General Physiology

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“…The Kd values obtained in the present study are much lower than reported before: 50/M (binding of [3H]ADP to turkey gizzard heavy meromyosin; Greene & Sellers, 1987); 100-300 /tM (inhibition of maximal shortening velocity in thiophosphorylated guinea-pig taenia coli fibre; Arner, Hellstrand & Ruiegg, 1987); 200,aM (in vitro motility assay using thiophosphorylated smooth muscle myosin; Warshaw & Trybus, 1991); 18-400 /tM (skeletal muscle;Marston, 1973;Cooke & Pate, 1985;Schoenberg & Eisenberg, 1987;Dantzig et al 1991). On the other hand, Kd values of ADP binding to cross-bridges are also low in cardiac myofibrils (7 AM; Johnson & Adams, 1984).…”

Section: High Affinity Mgadp Binding To Cross-bridges In Smooth Musclementioning

confidence: 85%

“…The Kd was similar (1 4AtM) in smooth muscle permeabilized with ,-escin, a saponin ester that creates larger pores than a-toxin, indicating that the high affinity was not an artifact of slow MgADP diffusion. The Kd estimated by an alternative method (Schoenberg & Eisenberg, 1987), from the effects of varying the ATP concentration on the initial component of relaxation, was 0-9 /tM. Creatine phosphate (20 mM), in the absence of Ca2", relaxed muscles from rigor when the myosin light chains were unphosphorylated, and contracted the muscles with thiophosphorylated light chains (Fig.…”

Section: High Affinity Mgadp Binding To Cross-bridges In Smooth Musclementioning

confidence: 97%

“…To verify this surprisingly low Kd value, we also estimated it by using another method. An N-fold reduction in substrate concentration should have the same effect as adding a competitive inhibitor at a concentration of (N-1) x Ki (the inhibition constant), when the binding of ATP and ADP is non-co-operative (Schoenberg & Eisenberg, 1987). Since the amplitude of initial relaxation induced by a 6 3-fold reduction of ATP concentration was the same as the amplitude of relaxation by 1-3 mm ATP in the presence of 5/M MgADP, the calculated Ki was 0 9 /lM.…”

Section: Muga)dp and The Cross-bridge (I-clementioning

confidence: 99%

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The effects of MgADP on cross‐bridge kinetics: a laser flash photolysis study of guinea‐pig smooth muscle.

Nishiye

Somlyo

Török

1993

The Journal of Physiology

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SUMMARY1. The effects of AMgADP on cross-bridge kinetics were investigated using laser flash photolysis of caged ATP (P3-1(2-nitrophenyl) ethyladenosine 5'-triphosphate), in guinea-pig portal vein smooth muscle permeabilized with Staphylococcus aureus atoxin. Isometric tension and in-phase stiffness transitions from rigor state were monitored upon photolysis of caged ATP. The estimated concentration of ATP released from caged ATP by high-pressure liquid chromatography (HPLC) was 1P3 mM.2. The time course of relaxation initiated by photolysis of caged ATP in the absence of Ca2+ was well fitted during the initial 200 ms by two exponential functions with tine constants of. respectively, T1 = 34 ms and T2 = 1P2 s and relative amplitudes of 0 14 and 0 86. Multiple exponential functions were needed to fit longer intervals; the half-time of the overall relaxation was 0-8 s. The second order rate constant for cross-bridge detachment by ATP, estimated from the rate of initial relaxation, was 0A4-23 x 104 M-1 s-1.3. MgADP dose dependently reduced both the relative amplitude of the first component and the rate constant of the second component of relaxation. Conversely, treatment of muscles with apyrase. to deplete endogenous ADP, increased the relative amplitude of the first component. In the presence of MgADP, in-phase stiffness decreased during force maintenance, suggesting that the force per crossbridge increased. The apparent dissociation constant (Kd) of MgADP for the crossbridge binding site, estimated from its concentration-dependent effect on the relative amplitude of the first component. was 1P3/M. This affinity is much higher than the previously reported values (50-300 JtM for smooth muscle; 18-400 /tM for skeletal muscle: 7-10 /um for cardiac muscle). It is possible that the high affinity reflects the properties of a state generated during the co-operative reattachment cycle, rather than that of the rigor bridge.4. The rate constant of MgADP release from cross-bridges, estimated from its concentration-dependent effect on the rate constant of the second (T2) component, was 0'35-7'7 s-'. To the extent that reattachment of cross-bridges could slow relaxation even during the initial 200 ms. this rate constant may be an underestimate. § To whom all correspondence should be addressed.Ms 1080 2E. XISHIY-E AND OTHERS 5. Inorganic phosphate (Pi, 30 mM) did not affect the rate of relaxation during the initial -50 ms, but accelerated the slower phase of relaxation, consistent with a cyclic cross-bridge model in which Pi increases the proportion of cross-bridges in detached ('weakly bound') states. In the presence of 100 /tM MgADP, Pi (10-50 mM) predominantly accelerated the final slow phase of relaxation, rather than the initial (T1 and T2) components, and shortened the duration of the plateau phase that followed the initial rapid relaxation.6. Muscles, in which the myosin light chains were thiophosphorylated, relaxed during the initial 40-50 ms after photolysis of caged ATP at the same rate as muscles with non-thiophos...

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“…Various effects on tension have been observed when MgADP is added to the bathing medium of a fibre in rigor (Marston, Tregear, Rodger & Clark, 1979; Kawai, 1986;Schoenberg & Eisenberg, 1987). We sought to determine the influence of MgADP on rigor tension under conditions minimizing both low-level ATP contamination and mechanical artifacts associated with the solution changes.…”

Section: Rigor Tension In the Presence Of Mgadpmentioning

confidence: 99%

Cross‐bridge kinetics in the presence of MgADP investigated by photolysis of caged ATP in rabbit psoas muscle fibres.

Dantzig

Hibberd

Trentham

et al. 1991

The Journal of Physiology

139

126

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SUMMARY1. The interaction between MgADP and rigor cross-bridges in glycerol-extracted single fibres from rabbit psoas muscle has been investigated using laser pulse photolysis of caged ATP (P3-1(2-nitrophenyl)ethyladenosine 5'-triphosphate) in the presence of MgADP and following small length changes applied to the rigor fibre.2. Addition of 465 gM-MgADP to a rigor fibre caused rigor tension to decrease by 15-3 + 0 7 % (s.E.M., n = 24 trials in thirteen fibres). The half-saturation value for this tension reduction was 18+4 /SM (n = 23, thirteen fibres).3. Relaxation from rigor by photolysis of caged ATP in the absence of Ca2`was markedly slowed by inclusion of 20 /,M-2 mM-MgADP in the photolysis medium.4 10. Computer simulations of the cross-bridge reactions involving ADP release, MgATP binding, detachment, and reattachment into force-generating intermediates were fitted to the transients recorded following photolysis of caged ATP. In the absence of ADP the time course of the transients could be simulated using a simple model without strain-dependent rate constants and assuming that attached crossbridge states in rapid equilibrium with detached states ({AM.ATP} and { M ADP Pi exerted zero force. However, in the presence of MgADP the transients simulated with these assumptions showed a deeper tension dip following photolysis of caged ATP than the experimental records.11. Two explanations of this discrepancy are considered. In the first hypothesis, rigor cross-bridges are assumed to be distributed over a wide range of forces, including negative forces, and ADP dissociates more rapidly from negatively strained cross-bridges than from positively strained ones. In the presence of MgADP, rapid detachment of the negatively strained cross-bridges limits the magnitude of tension dip following ATP release.12.

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ADP binding to myosin cross-bridges and its effect on the cross-bridge detachment rate constants.

Cited by 33 publications

References 33 publications

Tension transients initiated by photogeneration of MgADP in skinned skeletal muscle fibers.

Tension transients initiated by photogeneration of MgADP in skinned skeletal muscle fibers.

The effects of MgADP on cross‐bridge kinetics: a laser flash photolysis study of guinea‐pig smooth muscle.

Cross‐bridge kinetics in the presence of MgADP investigated by photolysis of caged ATP in rabbit psoas muscle fibres.

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