Direct interaction between troponin and myosin enhances the ATPase activity of heavy meromyosin

Biologia ◽  
2017 ◽  
Vol 72 (6) ◽  
Author(s):  
Nazanin Bohlooli Ghashghaee ◽  
King-Lun Li ◽  
Wen-Ji Dong
Keyword(s):  
Atpase Activity ◽  
Heart Muscle ◽  
Direct Interaction ◽  
Heavy Meromyosin ◽  
Thin Filaments ◽  
Cross Bridge ◽  
The Cross ◽  
Contractility Of The Heart

AbstractContractility of the heart muscle is a result of sliding movements between thick and thin filaments, produced by interactions between actin and myosin during the cross-bridge cycle. Activation of the myofilament is triggered by Ca

The Z band in skeletal muscle in rigor exhibits the activated lattice form

1989 ◽  
Vol 47 ◽  
pp. 252-253
Author(s):  
R. J. Edwards
Keyword(s):  
Skeletal Muscle ◽  
Cross Sections ◽  
Active Tension ◽  
Thin Filaments ◽  
Cross Bridge ◽  
The Cross ◽  
Cross Bridges ◽  
Glycerinated Muscle

The Z band of skeletal muscle is a tetragonal array of interdigitating thin filaments from adjacent sarcomeres held together by cross connecting filaments. Two visually unique forms of the Z band (small square, ss, and basketweave, bw) can be observed by TEM of cross sections. The ss form is found in relaxed muscle and the bw is found in maximally activated muscle. The average Z spacing in the bw form is 20% largerthan in the ss form. There is a correlation between active tension and the form of the Z band. This correlation suggests that cross bridge binding in the A band is directly related to the form of the Z band. In rigor, the cross bridges are completely bound; therefore, we predicted that the Z band would exhibit the bw form. To test this hypothesis we compared unstimulated muscle to glycerinated muscle in rigor.

Rate of heat production related to degree of filament overlap in chick ALD muscle

1977 ◽  
Vol 233 (1) ◽  
pp. C1-C7 ◽  
Author(s):  
Y. Matsumoto ◽  
A. M. McPhedran
Keyword(s):  
Heat Production ◽  
Length Change ◽  
Heat Liberation ◽  
Heavy Meromyosin ◽  
Thin Filaments ◽  
Cross Bridge ◽  
Single Cross ◽  
Anterior Latissimus Dorsi ◽  
Cross Bridges ◽  
Degree Of Overlap

The anterior latissimus dorsi (ALD) of chicks (2 wk old) was examined for rate of heat liberation when the muscle was reversibly stretched from L0 to about 1.6 L0. The "plateau" forces of isometric tetani were related to the corresponding rates of heat liberation. Presumably, in this region of length change the degree of overlap between the thick and thin filaments is changing. If the amount of overlap is known, the number of heavy meromyosin cross bridges in activity can be estimated. From this information, the amount of liberated energy can be calculated for a single cross-bridge cycling. In all of our measurements, there was heat production even at muscle lengths so great that no filament overlap would have to be assumed. This finding was incorported into the estimate for energy release per cross-bridge cycling.

scholarly journals The cross-bridge cycle and skeletal muscle fatigue

2008 ◽  
Vol 104 (2) ◽  
pp. 551-558 ◽  
Author(s):  
Robert H. Fitts
Keyword(s):  
Peak Power ◽  
Molecular Mechanisms ◽  
Fiber Type ◽  
Low Ph ◽  
Forward Rate ◽  
Maximal Velocity ◽  
Functional Changes ◽  
Cross Bridge ◽  
The Cross

The functional correlates of fatigue observed in both animals and humans during exercise include a decline in peak force (P0), maximal velocity, and peak power. Establishing the extent to which these deleterious functional changes result from direct effects on the myofilaments is facilitated through understanding the molecular mechanisms of the cross-bridge cycle. With actin-myosin binding, the cross-bridge transitions from a weakly bound low-force state to a strongly bound high-force state. Low pH reduces the number of high-force cross bridges in fast fibers, and the force per cross bridge in both fast and slow fibers. The former is thought to involve a direct inhibition of the forward rate constant for transition to the strong cross-bridge state. In contrast, inorganic phosphate (Pi) is thought to reduce P0 by accelerating the reversal of this step. Both H+ and Pi decrease myofibrillar Ca2+ sensitivity. This effect is particularly important as the amplitude of the Ca2+ transient falls with fatigue. The inhibitory effects of low pH and high Pi on P0 are reduced as temperature increases from 10 to 30°C. However, the H+-induced depression of peak power in the slow fiber type, and Pi inhibition of myofibrillar Ca2+ sensitivity in slow and fast fibers, are greater at high compared with low temperature. Thus the depressive effects of H+ and Pi at in vivo temperatures cannot easily be predicted from data collected below 25° C. In vitro, reactive oxygen species reduce myofibrillar Ca2+ sensitivity; however, the importance of this mechanism during in vivo exercise is unknown.

scholarly journals Calcium-Dependent Myosin from Insect Flight Muscles

1974 ◽  
Vol 63 (5) ◽  
pp. 553-563 ◽  
Author(s):  
William Lehman ◽  
Belinda Bullard ◽  
Kathleen Hammond
Keyword(s):  
Atpase Activity ◽  
Insect Flight ◽  
Calcium Regulation ◽  
Regulatory Proteins ◽  
Myosin Molecule ◽  
Thin Filaments ◽  
Actomyosin Atpase ◽  
Calcium Dependent ◽  
Regulatory Systems ◽  
Flight Muscles

Calcium regulation of the insect actomyosin ATPase is associated with the thin filaments as in vertebrate muscles, and also with the myosin molecule as in mollusks. This dual regulation is demonstrated using combinations of locust thin filaments with rabbit myosin and locust myosin with rabbit actin; in each case the ATPase of the hybrid actomyosin is calcium dependent. The two regulatory systems are synergistic, the calcium dependency of the locust actomyosin ATPase being at least 10 times that of the hybrid actomyosins described above. Likewise Lethocerus myosin also contains regulatory proteins. The ATPase activity of Lethocerus myosin is labile and is stabilized by the presence of rabbit actin. Tropomyosin activates the ATPase of insect actomyosin and the activation occurs irrespective of whether the myosin is calcium dependent or rendered independent of calcium.

Skeletal muscle force and actomyosin ATPase activity reduced by nitric oxide donor

1997 ◽  
Vol 83 (4) ◽  
pp. 1326-1332 ◽  
Author(s):  
William J. Perkins ◽  
Young-Soo Han ◽  
Gary C. Sieck
Keyword(s):  
Nitric Oxide ◽  
Mechanical Properties ◽  
Atpase Activity ◽  
Muscle Force ◽  
Isometric Force ◽  
Nitric Oxide Donor ◽  
No Donor ◽  
Single Fibers ◽  
Actomyosin Atpase ◽  
Cross Bridge

Perkins, William J., Young-Soo Han, and Gary C. Sieck.Skeletal muscle force and actomyosin ATPase activity reduced by nitric oxide donor. J. Appl. Physiol.83(4): 1326–1332, 1997.—Nitric oxide (NO) may exert direct effects on actin-myosin cross-bridge cycling by modulating critical thiols on the myosin head. In the present study, the effects of the NO donor sodium nitroprusside (SNP; 100 μM to 10 mM) on mechanical properties and actomyosin adenosinetriphosphatase (ATPase) activity of single permeabilized muscle fibers from the rabbit psoas muscle were determined. The effects of N-ethylmaleimide (NEM; 5–250 μM), a thiol-specific alkylating reagent, on mechanical properties of single fibers were also evaluated. Both NEM (≥25 μM) and SNP (≥1 mM) significantly inhibited isometric force and actomyosin ATPase activity. The unloaded shortening velocity of SNP-treated single fibers was decreased, but to a lesser extent, suggesting that SNP effects on isometric force and actomyosin ATPase were largely due to decreased cross-bridge recruitment. The calcium sensitivity of SNP-treated single fibers was also decreased. The effects of SNP, but not NEM, on force and actomyosin ATPase activity were reversed by treatment with 10 mMdl-dithiothreitol, a thiol-reducing agent. We conclude that the NO donor SNP inhibits contractile function caused by reversible oxidation of contractile protein thiols.

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