Characterization of components of inhibitory-factor (troponin B) preparations of the myofibril

The relaxing protein system and the regulation of the myofibrillar adenosine triphosphatase

“…In contrast with the inhibition obtained with the complete relaxing protein system this inhibition is insensitive to Ca2+. The inhibitory factor is the main active inhibitory component of troponin B preparations obtained by Hartshorne & Mueller (1968), which also have been shown to contain the 37000-dalton component (Wilkinson et al 1971). It is probably identical with the troponin fraction 2 reported by Greaser & Gergely (1971).…”

“…It now appears unlikely that troponin is a unique entity, but is probably a complex of three main protein components, the relative amounts of which are determined by the method of preparation. These have been described as the calcium-sensitizing factor, the inhibitory factor and a protein of molecular weight 37000, the precise function of which is as yet undetermined (Schaub & Perry, 1971; Wilkinson, Perry, Cole & Trayer, 1971).…”

“…Ebashi et al (1971) claim complete reconstitution of the relaxing protein system with tropomyosin, troponin I and troponin II. Greaser & Gergely (1971), however, report results that suggest that, in addition to tropomyosin, inhibitory factor and calcium-sensitizing factor, a 35000-dalton component, troponin fraction 3 (possibly corresponding to the 37000dalton component described by Wilkinson et al 1971) is also required. In our hands reconstitution of the relaxing protein system has been obtained in some circumstances with tropomyosin, inhibitory factor and calcium-sensitizing factor alone.…”

The interaction of the calcium-binding protein (troponin C) with bivalent cations and the inhibitory protein (troponin I)

“…It is now well established that the target protein for Ca2+ in the troponin complex is the calciumbinding protein, troponin C (Hartshorne & Mueller, 1968;Schaub & Perry, 1969;Wilkinson et al, 1971Wilkinson et al, , 1972Greaser & Gergely, 1971;Ebashi et al, 1971;Ebashi, 1972;Drabikowski et al, 1971;Murray & Kay, 1971). The changes in physical properties that have been reported as associated with the binding of Ca2+ by the troponin complex (Fuchs, 1971;Wakabayashi & Ebashi, 1968) probably reflect modifications in the structure of the calcium-binding-protein component itself.…”

Subunit structure and biological activity of tropomyosin B from different muscle types

“…In polyacrylamide-gel isoelectric focusing and electrophoresis in 6M-urea and 15mM-mercaptoethanol in tris-glycine buffer, pH8.5, tropomyosin from rabbit white skeletal muscle free of the '37000 component' of the troponin complex (Wilkinson et al, 1971) separated into two bands ofsimilar mobility. This pattern was observed on electrophoresis in 6 Murea and in sodium dodecyl sulphate in the presence of thiol compounds and after carboxymethylation.…”