Structural changes in actin-containing filaments of muscle

Vibert, Peter; Haselgrove, John C.; Lowy, J.; Poulsen, F. Reibke

doi:10.1016/s0022-2836(72)80036-6

Cited by 128 publications

(36 citation statements)

References 21 publications

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“…The evidence for cooperative behaviour of cross-bridge binding in smooth muscle is limited at present. Data from X-ray diffraction of smooth muscle fibres suggest that tropomyosin changes its position on actin when muscles enter into the rigor state [4,46]. Release of ATP from caged-ATP in skinned muscle in rigor causes a transient contraction [3,39].…”

Section: Discussionmentioning

confidence: 99%

The effects of caldesmon extraction on mechanical properties of skinned smooth muscle fibre preparations

Malmqvist

Arner

Makuch

et al. 1996

Pflugers Arch - Eur J Physiol

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The role of caldesmon in the regulation of smooth muscle contraction was investigated in chemically skinned smooth muscle fibres from the guinea-pig taenia coli. A 19-kDa C-terminal fragment of caldesmon gave a minor (<5%) reduction of force in fully thiophosphorylated fibres, but reduced force by about 50% at intermediate activation levels without affecting the level of light chain phosphorylation. An extraction procedure was developed using incubation in solutions containing high Mg2+ concentrations. Protein analysis revealed a selective decrease in the amount of caldesmon in the fibres. Maximal active force per cross-sectional area was unaffected. The Ca2+ dependence of active force was shifted towards lower Ca2+ concentrations and became less steep. The effects of extraction of caldesmon could in part be reversed by incubation in a solution containing purified caldesmon. The results are consistent with the hypothesis that caldesmon in smooth muscle thin filaments inhibits force generation and plays a role in regulating cooperative attachment of cross-bridges at sub-maximal levels of activation in smooth muscle.

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Section: Discussionmentioning

confidence: 99%

The effects of caldesmon extraction on mechanical properties of skinned smooth muscle fibre preparations

Malmqvist

Arner

Makuch

et al. 1996

Pflugers Arch - Eur J Physiol

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“…During contraction there is an increase in the intensity of both the 5.9 nm the 5.1 nrn layer-lines due to the binding of myosin heads to actin (Vibert et al, 1972;Haselgrove, 1975;Matsubara et al, 1984b). Experiments at different sarcomere lengths (Kress et aI., 1986) revealed that the enhancement of the 5.9 nm layer-line arises both from crossbridge attachment and conformational changes of the regulatory proteins of the thin filament, while changes on the 5.1 nm actin layer-line appear to arise from crossbridge attachment alone.…”

Section: Tension Generation and The Increase In The Intensities Of Thmentioning

confidence: 99%

X-ray diffraction studies on thermally induced tension generation in rigor muscle

Rapp

Davis

1996

J Muscle Res Cell Motil

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Muscle fibres in the rigor state and free of nucleotide contract if heated above their physiological working temperature. Kinetic studies on the mechanism of this process, termed rigor contraction, indicate that it has a number of features in common with the contraction of maximally Ca2+ activated fibres. De novo tension generation appears to be associated with a single, tension sensitive, endothermic step in both systems. Rigor contraction differs in that steps associated with crossbridge attachment and detachment are absent. We investigated structural changes associated with rigor contraction using X-ray diffraction. Overall changes in the low angle X-ray diffraction pattern were surveyed using a two-dimensional image plate. Reversible changes in the diffraction pattern included a 28% decrease in intensity of the 14.5 nm meridional reflection, a 12% increase in intensity of 5.9 nm actin layer-line and a somewhat variable 34% increase in intensity of 5.1 nm actin layer-line in laser temperature-jump experiments. When fibres were heated with a temperature ramp, we found that a 70% decrease in intensity of the myosin-related meridional reflection at (14.5 nm)-1 correlated with tension generation. A similar decrease in intensity of the 14.5 nm reflection is seen during tension recovery following a step change in the length of maximally Ca2+ activated fibres. Signals both from actin and actin-bound myosin heads contribute to the 5.1 and 5.9 nm actin layer-lines. Our observed changes in intensity are interpreted as contraction-associated changes in crossbridge shape and/or position on actin.

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“…X-ray diffraction studies of changes in the tropomyosin reflections upon activation (7)(8)(9)(10) do not distinguish whether the indicated movement of tropomyosin upon activation controls the number of turning-over cross-bridges or, alternatively, controls cross-bridge turnover kinetics.…”

mentioning

confidence: 99%

Effect of Ca2+ on cross-bridge turnover kinetics in skinned single rabbit psoas fibers: implications for regulation of muscle contraction.

Brenner

1988

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

549

570

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The effect of Ca2" upon the rate constant of force redevelopment following a period of isotonic shortening with immediate restretch to the starting sarcomere length was studied in rabbit psoas fibers at 5TC. Control experiments support the assumption that the rate constant of force redevelopment represents isometric cross-bridge turnover kinetics.(fapp + gmp), where fapp and gapp are the rate constants characterizing the transitions from the non-force-generating states to the force-generating states and back to the non-forcegenerating states, respectively. Parallel measurements of the rate constant of force redevelopment and of force, stiffness, and fiber ATPase during isometric contraction allow the effect of Ca2" uponfapp and gpp to be determined. Analysis reveals that Ca2 " has a marked effect upon fappq while g,,pp remains approximately unchanged. Furthermore, in the range above 25-30% of maximum Ca2 activation, regulation of force, stiffness, and ATPase is mediated through changes in fppy Below this range, however, it cannot be ruled out that, in addition, cross-bridges are also switched in and out of the turnover process ("recruitment"). As a consequence of regulation through turnover kinetics, both Ca2" sensitivity and the slope of force-pCa relations are shown to be affected by the ratio fa,,/gapp, which may represent an important mechanism of modulation of contractile function in addition to modulation through changes within the regulatory protein system. It is generally believed that muscle contraction occurs upon cyclic interaction between the myosin-and the actincontaining filaments, mediated by parts of the myosin molecules, termed cross-bridges. According to the cross-bridge model of Huxley (1), while hydrolyzing ATP, cross-bridges cycle between two states: a force-generating state in which cross-bridges are attached to actin and a non-forcegenerating state in which cross-bridges are detached from actin. In vertebrate striated muscle, cross-bridge action is controlled by Ca2 + through the regulatory proteins troponin and tropomyosin, which are located within the actin filaments (2). According to the cross-bridge model of Huxley (1), the increase in isometric force with Ca2" (e.g., ref. 3) is attributed to the increase in number of cross-bridges attached to actin in the force-generating state, whereas relaxation occurs when cross-bridges accumulate in the nonforce-generating state. Two mechanisms were proposed for Ca2 + activation to change the number of cross-bridges in the force-generating state. According to Podolsky and Teichholz (4), Ca2+ acts in an all-or-none fashion. Depending on the state of the regulated actin units, cross-bridges may either be cycling with fixed turnover kinetics or may not cycle at all; i.e., cross-bridges are switched in and out of the turnover process (simple "on/off switch" or "recruitment"). In this model, the increase in isometric force directly reflects the increase in the number of turning-over cross-bridges. Alternatively, Julian (5) proposed that Ca2+ ...

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Structural changes in actin-containing filaments of muscle

Cited by 128 publications

References 21 publications

The effects of caldesmon extraction on mechanical properties of skinned smooth muscle fibre preparations

The effects of caldesmon extraction on mechanical properties of skinned smooth muscle fibre preparations

X-ray diffraction studies on thermally induced tension generation in rigor muscle

Effect of Ca2+ on cross-bridge turnover kinetics in skinned single rabbit psoas fibers: implications for regulation of muscle contraction.

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