Characterization of a Nucleotide Kinase Encoded by Bacteriophage T7

摘要: Gene 1.7 protein is the only known nucleotide kinase encoded by bacteriophage T7. The enzyme phosphorylates dTMP and dGMP to dTDP dGDP, respectively, in presence of a phosphate donor. donors are dTTP, dGTP, ribo-GTP as well thymidine guanosine triphosphate analogs ddTTP, ddGTP, dITP. found solution 256-kDa complex consisting ∼12 monomers gene protein. two molecular weight forms co-purify complex, but each form has nearly identical activity. Although does not require metal ion for its activity, Mg2+ reaction mixture results either inhibition or stimulation rate reactions depending on substrates used. Both reversible. Neither nor dGDP acceptor nucleoside donors. exhibits different equilibrium patterns toward deoxyguanosine substrates. Km 4.4 × 10−4 m obtained with dTTP ∼3-fold higher than that dGTP (1.3 m), indicating concentration required saturate enzyme. Inhibition studies indicate competitive relationship between both dGMP, whereas appears have mixed type kinase. Studies suggest functions donor positive effector reaction.