[Troponin T kinase: possible relationship to casein kinases of the G type]

Troponin T kinase utilizes ATP and GTP as substrates for the protein kinase reaction. When phosvitin is used as substrate, the enzyme activity increases with an increase in the ionic strength up to 0.2-0.3 M KCl. The pH optimum for the enzyme lies at 8-9. Ultracentrifugation in sucrose density gradient showed that the sedimentation coefficient of troponin T kinase is 9.5 S. The Stocks radius determined by gel-filtration is equal to 49 A. The molecular weight of the enzyme calculated from the given values of the Stocks radius and sedimentation coefficient is 184,000. This is indicative of the oligomeric structure of the enzyme and suggests that the stoicheiometry of the enzyme subunits having mol. weights of 50,000, 46,000 and 31,000 is other than 1:1:1. Troponin T kinase is capable of autophosphorylation; the phosphorylation process involves only the protein with mol. weight of 31,000. The data obtained suggest that troponin T kinase can be referred to casein kinases of G type and may participate in translation processes.