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Crossbridge and filament compliance in muscle: implications for tension generation and lever arm swing
- Source :
- Journal of Muscle Research and Cell Motility. 31:245-265
- Publication Year :
- 2010
- Publisher :
- Springer Science and Business Media LLC, 2010.
-
Abstract
- The stiffness of myosin heads attached to actin is a crucial parameter in determining the kinetics and mechanics of the crossbridge cycle. It has been claimed that the stiffness of myosin heads in the anterior tibialis muscle of the common frog (Rana temporaria) is as high as 3.3 pN/nm, substantially higher than its value in rabbit muscle (~1.7 pN/nm). However, the crossbridge stiffness measurement has a large error since the contribution of crossbridges to half-sarcomere compliance is obtained by subtracting from the half-sarcomere compliance the contributions of the thick and thin filaments, each with a substantial error. Calculation of its value for isometric contraction also depends on the fraction of heads that are attached, for which there is no consensus. Surprisingly, the stiffness of the myosin head from the edible frog, Rana esculenta, determined in the same manner, is only 60% of that in Rana temporaria. In our view it is unlikely that the value of such a crucial parameter could differ so substantially between two frog species. Since the means of the myosin head stiffness in these two species are not significantly different, we suggest that the best estimate of the stiffness of the myosin heads for frog muscle is the average of these data, a value similar to that for rabbit muscle. This would allow both frog and rabbit muscles to operate the same low-cooperativity mechanism for the crossbridge cycle with only one or two tension-generating steps. We review evidence that much of the compliance of the myosin head is located in the pliant region where the lever arm emerges from the converter and propose that tension generation ("tensing") caused by the rotation and movement of the converter is a separate event from the passive swinging of the lever arm in its working stroke in which the strain energy stored in the pliant region is used to do work.
- Subjects :
- Sarcomeres
Ranidae
Physiology
Movement
Edible frog
macromolecular substances
Isometric exercise
Myosins
Biochemistry
Rana
Protein filament
Myosin head
CrossBridge
Isometric Contraction
biology.animal
Myosin
Animals
Muscle, Skeletal
Cytoskeleton
Actin
biology
Chemistry
Muscles
Cell Biology
Anatomy
Actins
Elasticity
Biomechanical Phenomena
Models, Structural
Actin Cytoskeleton
Muscle Tonus
Biophysics
Thermodynamics
Rabbits
Subjects
Details
- ISSN :
- 15732657 and 01424319
- Volume :
- 31
- Database :
- OpenAIRE
- Journal :
- Journal of Muscle Research and Cell Motility
- Accession number :
- edsair.doi.dedup.....825a7c890212fd7c3ac517f5b2d81459