The in vitro ATPases of bacteriophage lambda terminase and its large subunit, gene product A. The relationship with their DNA helicase and packaging activities.

The bacteriophage lambda terminase is composed of two subunits, gpNu1 and gpA. In vitro, the holoenzyme is a site-specific endonuclease, helicase, ATPase, and can package lambda DNA into proheads. gpA possesses ATPase and helicase activities which are similar to those of the holoenzyme. Both terminase and gpA can hydrolyze a wide range of deoxyribo- and ribonucleoside triphosphates to inorganic phosphate and the corresponding diphosphate. Nucleoside diphosphates are not substrates for either protein. ATPase of both proteins is stimulated by double-stranded DNA. The ATPase of gpA is protein concentration-dependent, while that of terminase is not. Helicase activity of both proteins is not concentration-dependent, and requires a hydrolyzable triphosphate. ATP, dATP, and GTP supported helicase activity, while adenosine 5'-(beta, gamma-methylene)triphosphate, adenosine 5'-3-O-(thio)triphosphate, ADP, CTP, and UTP did not. The kinetic parameters of ATPase and helicase activities were similar for both proteins, but packaging with terminase was optimal only at a significantly higher level of ATP. Packaging was detectable at significant levels with CTP and UTP, but not with GTP. Packaging also differed from ATPase and helicase in the utilization of divalent metal cations and susceptibility to various inhibitors.