Periodic Distribution of Troponin along the Thin Filament*

Otsuki, Ikuto; Masaki, Τοmoh; Nonomura, Yoshiaki; Ebashi, Setsuro

doi:10.1093/oxfordjournals.jbchem.a128619

Cited by 147 publications

(45 citation statements)

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“…It now appears that there is more than one calcium-binding site and more than one class of calcium-binding sites 31 ' 32 on the regulating protein troponin, which is located on the thin filaments. 33 There is even the possibility that vertebrate thick filaments have regulating sites that could bind calcium. 34 In the model, however, the further simplifying assumption is made that there is only one class of regulating sites and that the proportion of these sites filled with calcium, after a single stimulus, could be approximated by the following second-order equation: (6) where y is the proportion filled at time, /; a 0 and b p are constants; and a and /} are rate constants governing the filling and emptying of the sites.…”

Section: Computer Model Of Muscle Behaviormentioning

confidence: 99%

The concept of active state in striated muscle.

Julian¹,

Moss²

1976

Circulation Research

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FOR THE purposes of this review, it will be helpful to consider the simple block diagram of a striated muscle system shown in Figure 1. The system has been generalized, in order to be applicable to heart muscle, by including an inotropic state mechanism. The parallel elastic component is necessary to account for resting tension. However, neither of these elements will be discussed further. According to the classical model for muscle contraction proposed by Hill, 1 a contracting muscle can be represented by a contractile component (CC) in series with a series elastic component (SEC). In the resting state, the CC is freely extensible, whereas in the active state it is supposed to resist strongly any attempt to suddenly change its length. The properties of the active CC are such that its force-velocity behavior can be described by the following equation:where Pis the force, V is the velocity of shortening and a and b are constants. The use of P 0J , where / is time, can be explained as follows. During a steady state isometric contraction, as in a tetanus, successive stimuli serve to keep the active state at its maximum level, indicated by the tetanic P o -In this case there is no need for the subscript t in Equation 1, because P o is time-invariant. However, in a twitch the peak developed isometric force does not attain the tetanic level. Hill 2 knew from his thermal measurements that heat production starts off at its maximum rate very soon after a stimulus and before any mechanical response is detectable. He therefore reasoned that the transition in the CC from rest to a fully "active state" following a single stimulus was very rapid, so that the active state was completely developed. Relaxation was produced by a slower decline of the active state to its resting level. Hill 2 defined the intensity of the active state at any instant in time to be equal to the magnitude of the developed force when the velocity of shortening of the CC was zero; that is, in Equation 1, P o> , = P when V = 0. Using this definition, and expressing the force of the CC, P, relative to the tetanic P o , it can be seen that the active state level varies between 0 and 1.In view of the fact that Levin and Wyman 3 showed that

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Section: Computer Model Of Muscle Behaviormentioning

confidence: 99%

The concept of active state in striated muscle.

Julian¹,

Moss²

1976

Circulation Research

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“…Troponin, the regulatory protein in vertebrate striated muscle, is associated with actin and tropomyosin in the thin filaments [1,2]. It is through troponin that calcium ion released from the sarcoplasmic reticulum regulates contraction in these muscles by controlling actin-myosin interaction.…”

mentioning

confidence: 99%

Regulation of Muscle Contraction: Binding of Troponin and Its Components to Actin and Tropomyosin

Hitchcock

1975

European Journal of Biochemistry

107

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The binding of troponin components to actin and tropomyosin has been studied by cosedimentation with actin and affinity chromatography. It is shown that troponin binds to actin and tropomyosin in the presence and absence of calcium but the binding to actin is sensitive to ionic strength. Troponin-I + C binds to actin-tropomyosin in the absence of calcium but not to actin or tropomyosin alone.Troponin-I binds to actin and the binding is improved in the presence of tropomyosin even though troponin-I does not bind to tropomyosin alone. Troponin-C does not bind to actin or tropomyosin. The results suggest that the binding of troponin by actin is influenced by tropomyosin. A model of regulation by troponin is proposed.

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“…Several studies (Corsi et al, 1967;Endo ^ al., 1966;Perry and Corsi, 1958) have shown that tropomyosin is also located in the thin filament, and recently, Ebashi and co-workers (Endo et aj^., 1966;Ohtsuki et al», 1967) have presented evidence that troponin is distributed along the length of the thin filament with a periodicity of ^00A°. Since neither troponin nor tropo myosin were seen in Hanson and Lowy's (1963) micrographs of negatively stained thin filaments, the exact distribution of actin, tropomyosin and troponin in the thin filament is presently unclear.…”

Section: Muscle Biologymentioning

confidence: 99%

Subcellular events associated with the development and release of isometric tension in post-mortem bovine, rabbit and porcine skeletal muscle

Busch

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Periodic Distribution of Troponin along the Thin Filament*

Cited by 147 publications

References 0 publications

The concept of active state in striated muscle.

The concept of active state in striated muscle.

Regulation of Muscle Contraction: Binding of Troponin and Its Components to Actin and Tropomyosin

Subcellular events associated with the development and release of isometric tension in post-mortem bovine, rabbit and porcine skeletal muscle

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