A defined system for in vitro λ DNA packaging

Abstract

We constructed a defined in vitro system for packaging λ DNA which is composed of purified proheads, the noncapsid proteins terminase and gpFI, and the Escherichia coli DNA binding/bending protein IHF. The defined packaging system: (i) Is free from endogenous ATP, DNAs, and DNases and (ii) packages 30% of the input mature λ DNA efficiently. In this defined packaging system, IHF and gpFI make modest contributions to packaging efficiency. The defined packaging reactions showed that DNA packaging gave a linear response to the concentration of mature λ DNA and terminase. DNA packaging showed a sigmoidal relationship with respect to the concentration or ATP and proheads. © 1995 Academic Press, Inc.