Modulation of troponin C affinity for the thin filament by different cross-bridge states in skinned skeletal muscle fibers

2008 ◽  
Vol 456 (6) ◽  
pp. 1177-1187 ◽  
Author(s):  
José Renato Pinto ◽  
Tiago Veltri ◽  
Martha M. Sorenson
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Muscle Fibers ◽  
Troponin C ◽  
Cross Bridge ◽  
Skeletal Muscle Fibers

scholarly journals Ca2+ and Cross-Bridge-Induced Changes in Troponin C in Skinned Skeletal Muscle Fibers: Effects of Force Inhibition

1999 ◽  
Vol 76 (3) ◽  
pp. 1480-1493 ◽  
Author(s):  
D.A. Martyn ◽  
C.J. Freitag ◽  
P.B. Chase ◽  
A.M. Gordon
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Troponin C ◽  
Cross Bridge ◽  
Skeletal Muscle Fibers ◽  
Induced Changes

pH dependence of myosin binding-induced activation of the thin filament in cardiac myocytes and skeletal fibers

1996 ◽  
Vol 270 (3) ◽  
pp. H1008-H1014 ◽  
Author(s):  
J. M. Metzger
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Myocytes ◽  
Thin Filament ◽  
Ph Dependence ◽  
Muscle Fibers ◽  
Isometric Tension ◽  
Experimental Conditions ◽  
Skeletal Muscle Fibers ◽  
Myosin Binding ◽  
Fast Twitch

The pH dependence of myosin binding-induced thin filament activation was determined in permeabilized cardiac myocytes and slow- and fast-twitch single skeletal muscle fibers by experimental lowering of [MgATP] in the Ca(2+)-free solutions bathing the permeabilized preparations. As the pS (where S is [MgATP] and pS is -log[MgATP]) was increased from 3.0 to 8.0, isometric tension increased to a peak value in the pS range of 4.9-5.3. At pH 7.00, the transition from the relaxed to the activated rigor state was steep in cardiac myocytes [Hill value (nH) = 21.2 +/- 3.1 (SE)] and due to the apparent effect of strongly bound cross bridges to cooperatively activate the thin filament in the absence of added Ca2+. At pH 6.20, the steepness of the tension-pS relationship was markedly reduced (nH = 6.1 +/- 1.0) and the midpoint of the relationship (pS50) was shifted to higher pS values in cardiac myocytes. In comparison, reduced pH had no effect on the steepness or position of the tension-pS relationship in single slow- or fast-twitch skeletal muscle fibers. These findings suggest that myosin binding-induced activation of the thin filament is pH dependent in cardiac myocytes but not in skeletal muscle fibers under these experimental conditions in which Ca2+ is absent.

scholarly journals Effects of ramp shortening during linear phase of relaxation on [Ca2+]i in intact skeletal muscle fibers

1999 ◽  
Vol 276 (1) ◽  
pp. C152-C160 ◽  
Author(s):  
Yandong Jiang ◽  
Fred J. Julian
Keyword(s):  
Skeletal Muscle ◽  
Thin Filament ◽  
Sarcomere Length ◽  
Muscle Fibers ◽  
Linear Phase ◽  
Fixed Size ◽  
Skeletal Muscle Fibers ◽  
Straight Line ◽  
Sigmoidal Curve ◽  
Cross Bridges

The effects of shortening distance at V u, the unloaded shortening speed, and filament overlap on the amount of extra Ca2+ released during relaxation in muscle, as indicated by the bump area, were studied. Single, intact frog skeletal muscle fibers at 3°C were used. The myoplasmic free Ca2+ concentration ([Ca2+]i) was estimated by using fura 2 salt injected into the myoplasm. Ramps were applied, either at full overlap with different sizes or at varying overlaps with a fixed size, in the linear phase of relaxation. At full overlap, a plot of bump area vs. ramp size was fit by using a sigmoidal curve with one-half of the bump area equal to 25.9 nm. With a fixed ramp size of 100 nm/half-sarcomere, the plot of bump area vs. mean sarcomere length (SLm) was fit by a straight line intersecting the SLm axis at ∼3.5 μm, close to just no overlap. The results suggest that the transition in the distribution of attached cross bridges from the isometric case to one appropriate for unloaded shortening at V u is completed within 50 nm/half-sarcomere and support the view that attached cross bridges in the overlap zone influence the affinity of Ca2+for troponin C in the thin filament.

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