DNA-independent ATPase activity of the Trichoplusia ni granulovirus DNA helicase

DNA helicases of baculoviruses are essential for virus replication and have been implicated as molecular determinants of host range. Although these pr oteins contain seven motifs (I, Ia, II-VI) characteristic of DNA helicases, the two most important characteristics of helicases - duplex-DNA unwinding and ATPase activity - have not been demonstrated. In the present study, a recombinant putative DNA helicase (rP137) of Trichoplusia ni granulovirus ( TnGV) was purified from insect cells infected with a recombinant Autographa californica multicapsid nucleopolyhedrovirus that overproduced rP137, The rP137 protein exhibited an intrinsic DNA-independent ATPase activity that r equired Mg2+ as a co-factor, an activity that was reduced in the presence o f TnGV and phage lambda. DNAs, These results provide further evidence that baculovirus helicase genes encode proteins with biochemical properties simi lar to those of classical DNA helicases.