Skeletal and Cardiac Troponins and Their Components*

Publisher Website
Google Scholar
Abstract
Troponin was purified by ammonium sulfate salting-out in the presence of 5 M urea. Three major components of the purified troponin were separately eluted with different concentrations of LiCl from a DEAE-Sephadex column in the presence of 6 m urea. Their molecular weights estimated by gel electrophoresis with sodium dodecyl sulfate were approximately 17,000 (component α), 23,000 (component β), and 45,000 daltons (component γ). Only two components, α and β, were needed for reproducing the functional effects of original troponin on superprecipitation of trypsin-treated myosin B; an inhibition effect in the absence of calcium and an activation effect in its presence. Component β inhibited superprecipitation both in the absence and presence of calcium, thus being identified as an “inhibitory factor.” Component α was capable of removing the inhibition caused by component β. This removal occurred both in the presence and absence of calcium, but the concentration of component α required was much less in the presence of calcium than in its absence. Component α was thus identi-fied as a “calcium sensitizing factor.” This identification was further supported by the following experiment: Troponin was removed from skeletal myosin B by trypsin-treatment. Cardiac component α and skeletal component β were then recombined with the trypsin-treated skeletal myosin B. The myosin B thus reconstituted was found to be as sensitive as non-treated cardiac myosin B to the addition of strontium. Component γ, like component α, was capable of removing the inhibitory effect of component β. However, it was less effective than component a, and moreover, its effect of removing the inhibition was not improved by the presence of calcium. Because component y was very similar to component β in amino acid composition, it was temporarily suggested that component γ is a modified form or a dimer of com-ponent β. However, component γ is still the subject for a further investigation especially due to the following accounts: (a) The yield of component γ was better than that of either component α or β. (b) Preparations of component y often con-tained protein components with molecular weights different from 45,000 .

This publication has 0 references indexed in Scilit: