TEMPLATE-PRIMER-DEPENDENT INACTIVATION OF HUMAN PLACENTA DNA POLYMERASE α BY 2' ,3' -EPOXYADENOSINE 5'-TRIPHOSPHATE
V. N. PODUST, T. O. KOROBEINICHEVA, G. A. NEVINSKY, V. A. RIKHTER*, T. I. ABRAMOVA, O. I. LAVRIK
Novosibirsk Institute of Bioorganic Chemistry, Siberian Division of the Academy of Sciences of the USSR;* Institute of Nuclear Physics, Academy of Sciences of the Uzbek SSR, Tashkent
Abstract: Modification of the human placenta DNA polymerase α by 2',3'-epoxyadenosine -5'-triphosphate (eATP) was investigated. The latter binds to the protein both in absence and in presence of template-primer complex. However for inactivation of the enzyme, reagent-complementary template, primer and Me2+-ions are required. The inactivation is apparently due to the affinity modification of dNTP-binding site by eATP; covalent binding of the reagent off the enzyme's active site without affecting the DNA polymerase activity is also suggested.
The enzyme inactivation by eATP and its protection from inactivation in the presence of dATP were used to determine Km values of complexes of the enzyme with eATP (90 M.M) and dATP (1 μM), the latter value being 13-times lower than Km for dATP (13 μM) in the polymerisation reaction. Using the dependence of the DNA polymerase inactivation by eATP on the primer concentration, Kd for enzyme-primer complexes were estimated. The Kd value for d(pA)10 (0,33 μM) was close to Km value (0,43 μM) for this primer. eATP was concluded to be a useful reagent for estimating the efficiency of the complex formation of different ligands with dNTP- and primer-binding sites of DNA polymerase.
Russian Journal of Bioorganic Chemistry 1990, 16 (2):226-235