Use of an X-ray television for diffraction of the frog striated muscle

Matsubara, Ichiro; Yagi, Naoto; Hashizume, H.

doi:10.1038/255728a0

Cited by 58 publications

(31 citation statements)

References 5 publications

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“…These conclusions are in agreement with x-ray and stiffness observations of contracting muscle (15)(16)(17)(18) but are in disagreement with deductions from ESR studies of maleimide spin probes that suggest --20% of the crossbridges are actin-attached and that those that are attached are in the rigor orientation (3). The origin of these differences is unknown and may not be due to differences in orientation of the probe relative to the protein (spin probe compared with fluorescent probe) (19).…”

Section: Resultssupporting

confidence: 81%

Fraction of myosin cross-bridges bound to actin in active muscle fibers: estimation by fluorescence anisotropy measurements.

Burghardt¹,

Ajtai²

1985

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

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Time-resolved and steady-state fluorescence anisotropy measurements from fluorescence-labeled myosin cross-bridges in single glycerinated skeletal muscle fibers in rigor, relaxed, MgADP-induced, and contracting states have been made in order to estimate the fraction of actin-bound cross-bridges in active muscle. When the plane of polarization of the excitation light is perpendicular to the fiber axis and its propagation vector has a component parallel to this axis, actin-bound cross-bridge states, such as rigor and MgADPinduced, have time-zero and steady-state anisotropies that are substantially lower than has the relaxed state. This difference provides a means of determining the fraction of cross-bridges bound to actin in active isometric fibers, by comparing the fluorescence anisotropy from active fibers with the anisotropy from bound and unbound cross-bridges in static states. By assuming that the active cross-bridges are either bound (in the manner of rigor or MgADP-induced states) or relaxed, we estimate that >80% of the cross-bridges are actin-bound in active isometric fibers.In the investigation of whether muscle myosin cross-bridges or parts of cross-bridges rotate during impulsion, extrinsic probes attached to the cross-bridges have been used because of their sensitivity to rotation. In our laboratory, work with fluorescent probes has generally confirmed the occurrence of rotational transitions between actin-attached states (1, 2), as well as indicated a high percentage (=65%) of cross-bridge attachment to actin during isometric tension generation (2). However, the work of others, using spin labels, has contradicted both results; in regard to percent attachment, estimates from spin-label work have indicated -20% attachment (3). The discrepancy concerning percent attachment, h, seems to us a good one on which to focus, since it is a quantity that can be estimated by various methods. In previous reports, estimates of h were based on angle information from iodoacetylrhodamine labels that reacted with the fast-reacting thiol (SH-1) of subfragment 1 (S-1) of myosin. We now report measurements of h obtained by similar reaction of SH-1 with 5-[2-(iodoacetyl)aminoethyl]aminonaphthalene-1-sulfonic acid (1,5-IAEDANS).Recent work in our laboratory has shown that, with 1,5-IAEDANS specifically attached to SH-1, thermal motion of cross-bridges in muscle fibers in the nanosecond time domain can be detected by use of the time-resolved fluorescence-anisotropy decay (TRFAD) technique as applied to ordered biological assemblies (4,5). In a previous TRFAD study, evidence was presented for two distinct rotational motions of the cross-bridge about two different axes of rotation (5). The distinction of the two cross-bridge motions is achieved by orienting the fiber in the excitation beam so that in one case (the "vertical fiber"), the polarization anisotropy is sensitive to cross-bridge motions about axes perpendicular to the fiber axis; and in another case (the "horizontal fiber"), the polarization anisotropy is sen...

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Section: Resultssupporting

confidence: 81%

Fraction of myosin cross-bridges bound to actin in active muscle fibers: estimation by fluorescence anisotropy measurements.

Burghardt¹,

Ajtai²

1985

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

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“…The radial transfer of myosin heads in the maximally activated muscle (98 % of the transfer in rigor) was greater than that in the frog skeletal muscle during maximum tetanus (86-89%; Matsubara, Yagi & Hashizume, 1975). The increased transfer may be due to a local decrease in Mg ATP concentration in the activated preparation.…”

Section: Discussionmentioning

confidence: 84%

Lateral filamentary spacing in chemically skinned murine muscles during contraction.

Matsubara¹,

Umazume²,

Yagi³

1985

The Journal of Physiology

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SUMMARY1. A mouse toe muscle was chemically skinned with saponin and the 1,0 spacing of the hexagonal myofilament lattice at a sarcomere length of 2-5 Itm was measured with the X-ray-diffraction method. In the relaxed state, the 1,0 spacing was 40-8 nm.2. When the muscle was maximally activated at pCa 4 4, the spacing decreased to 38-4 nm. During contractions at lower calcium concentrations, the spacing decreased less. In rigor, the spacing decreased to almost the same extent as during maximum contraction, although the rigor tension was only 8 O of the maximum tension.3. When the spacing in relaxed muscle had been adjusted osmotically to about 38 nm, activation caused no further decrease in the spacing.4. The results support the view that the force responsible for the lattice shrinkage during contraction is produced by cross-bridges displaced from their optimum lateral positions.

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“…If this inference is correct, we can estimate the size of the motion induced by MgADP binding on the assumption that the compliant part of the cross-bridge is stretched by 4 nm on average during isometric contractions (Ford, Huxley & Simmons, 1977), 75% of the cross-bridges attached in rigor are attached during active contractions (Haselgrove & Huxley, 1973;Matsubara, Yagi & Hashizume, 1975;Goldman & Simmons, 1977; Fig. 12 of the present paper) and that the force-extension curve at the cross-bridge is linear (Ford et al 1977).…”

Section: Lenart J W Tanner and Y E Goldman Personal Communication)mentioning

confidence: 99%

“…17 (Webb et al 1986) and most cross-bridges are attached in activated isometric mnuscle (Haselgrove & Huxley, 1973;Matsubara et al 1975;Goldman & Simmons, 1977). Measurements of MgATP-induced cross-bridge dissociation, ATP hydrolysis, tension development and kinetics of Pi release (Goldman et al 1984b;Hibberd et al 1985;Ferenczi, 1986) have indicated that all of these steps are too fast to limit the overall cycling rate in activated isometric muscle.…”

Section: Simulation Of Interactions Between Paired Sitesmentioning

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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Use of an X-ray television for diffraction of the frog striated muscle

Cited by 58 publications

References 5 publications

Fraction of myosin cross-bridges bound to actin in active muscle fibers: estimation by fluorescence anisotropy measurements.

Fraction of myosin cross-bridges bound to actin in active muscle fibers: estimation by fluorescence anisotropy measurements.

Lateral filamentary spacing in chemically skinned murine muscles during contraction.

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

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