[Physico-chemical and enzymatic properties of contractile protein of rat liver mitochondria].

Some properties of the contractile protein of mitochondria in rat liver (mito-AM) and actomyosin (AM) have been comparatively studied. Mito-AM revealed the viscosity change as well as the precipitation test when ATP was added. The precipitation test rate proved to be higher in some cases than in case of AM. The characteristic feature for both enzymes was the inhibition of the enzymatic activity due to substrate abundance and the reaction product. According to their activating eff on ATP-ase of mito-AM, divalent cations can be placed in the following way: Ca2+ greater than greater than Mg2+greater than Mn2+greater than Zn2+. A similarity in the effect of p-chlormercuribenzoate, amitale and ouabain on mito-AM and AM is revealed. Spectrum analysis data (absorption and fluorescent spectra, fluorescence polarization) as well as different substrate specificity indicate the presence of certain differences in proteins studied. Purified mito-AM revealed a number of components with mollecular meights ranging from 12,500 to 87,000 under polyacrylamide gel electrophoresis in the presence of sodium dodecul sulphate. The 44,000 mollecular weight polypeptide chain was of muscle actin origin. The results obtained are discussed from the view point of protein functional characteristics.