scholarly journals The effect of partial extraction of troponin C on the elementary steps of the cross-bridge cycle in rabbit psoas muscle fibers

1996 ◽  
Vol 71 (5) ◽  
pp. 2759-2773 ◽  
Author(s):  
Y. Zhao ◽  
P.M. Swamy ◽  
K.A. Humphries ◽  
M. Kawai
Keyword(s):  
Muscle Fibers ◽  
Psoas Muscle ◽  
Troponin C ◽  
Rabbit Psoas ◽  
Elementary Steps ◽  
Cross Bridge ◽  
The Cross ◽  
Partial Extraction

BDM affects nucleotide binding and force generation steps of the cross-bridge cycle in rabbit psoas muscle fibers

1994 ◽  
Vol 266 (2) ◽  
pp. C437-C447 ◽  
Author(s):  
Y. Zhao ◽  
M. Kawai
Keyword(s):  
Equilibrium Constants ◽  
Muscle Fibers ◽  
Psoas Muscle ◽  
Isometric Tension ◽  
Activation Mechanism ◽  
Phosphate Binding ◽  
Rabbit Psoas ◽  
Cross Bridge ◽  
The Cross ◽  
Cross Bridges

The effect of 2,3-butanedione monoxime (BDM) on elementary steps of the cross-bridge cycle was studied with the sinusoidal analysis technique in skinned rabbit psoas muscle fibers. Our results showed that isometric tension and stiffness decreased progressively with an increase in the BDM concentration. The MgATP and MgADP binding constants increased 27 and 6 times, respectively, when BDM was increased from 0 to 18 mM, whereas the phosphate binding constant did not change significantly. The equilibrium constants of the ATP isomerization and detachment step were not sensitive to BDM, whereas the equilibrium constant of the attachment (power stroke) step decreased with BDM. Thus, in the presence of BDM, the number of attached cross bridges decreases; more cross bridges accumulate in the detached state, causing isometric tension and stiffness to decline. However, our detailed analysis shows that the decrease in the number of attached cross bridges is approximately 40%, which is not adequate to account for the 84% decrease in the isometric tension when 18 mM BDM was present. Therefore we suggest that a thin-filament activation mechanism is also affected by BDM.

scholarly journals Reversal of the cross-bridge force-generating transition by photogeneration of phosphate in rabbit psoas muscle fibres.

1992 ◽  
Vol 451 (1) ◽  
pp. 247-278 ◽  
Author(s):  
J A Dantzig ◽  
Y E Goldman ◽  
N C Millar ◽  
J Lacktis ◽  
E Homsher
Keyword(s):  
Psoas Muscle ◽  
Muscle Fibres ◽  
Rabbit Psoas ◽  
Cross Bridge ◽  
The Cross

Force, length, and Ca(2+)-troponin C affinity in skeletal muscle

1991 ◽  
Vol 261 (5) ◽  
pp. C787-C792 ◽  
Author(s):  
F. Fuchs ◽  
Y. P. Wang
Keyword(s):  
Skeletal Muscle ◽  
Protein Interactions ◽  
Muscle Fibers ◽  
Psoas Muscle ◽  
Troponin C ◽  
Force Generation ◽  
Fluorescence Probes ◽  
Protein Protein Interactions ◽  
Rabbit Psoas ◽  
Cross Bridges

On the basis of isotopic methods it has been found that force generation promotes increased Ca2+ binding to troponin C in cardiac muscle [P. Hofmann and F. Fuchs. Am. J. Physiol. 253 (Cell Physiol. 22): C541-C546, 1987] but not in skeletal muscle (J. Muscle Res. Cell Motil. 6: 477, 1985). However, studies with skinned rabbit psoas muscle fibers containing substituted fluorescent troponin C analogues indicate that force-generating cross bridges do promote increased Ca2+ binding in skeletal muscle (K. Guth and J. D. Potter. J. Biol. Chem. 262: 13627-13635, 1987). We have reexamined this question using a modified contraction-relaxation protocol in which Ca2+ binding to detergent-treated rabbit psoas fibers was measured either during steady-state force development or after relaxation was induced by one of two myosin ATPase inhibitors, vanadate or 2,3-butanedione monoxime. A standard double-isotope technique was used to measure Ca2+ binding. Another set of experiments was done in which force was reduced by releasing muscle fibers from sarcomere lengths of 2.4-2.6 microns to 1.5-1.7 microns, and bound Ca2+ was determined either before or after the release. No statistically significant effect of force generation or sarcomere length on Ca(2+)-troponin C affinity was observed. Thus the discrepancy remains between results obtained with isotopic and fluorescence methods. It is possible that in skinned fibers emission from fluorescence probes is more closely related to protein-protein interactions than to the amount of Ca2+ bound to troponin C.

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