Biological Sciences: Role of ATP in DNA Replication

Abstract

THE bacterial chromosome replicates in a semiconservative manner¹. This process may occur at the cell membrane^2,3. Efforts to study replication by means of purified DNA polymerases have failed to elucidate the mechanism of the in vivo process. Therefore, recent attempts have been made toward isolation of membrane-containing systems which more nearly approximate the properties of in vivo replication. Two different procedures have been used. One relies on hydrolysis of the cell wall by lysozyme, followed by gentle disruption of the spheroplast membrane so as to avoid shearing the replication apparatus^4,5. In a different approach, cells have been made permeable to nucleotides and other small molecules by treatment with toluene^6–8 or ether⁹. This permits incorporation studies with little alteration of the cell interior. Both of these procedures yield preparations that replicate bacterial or phage DNAs semiconservatively in the presence of ATP, as measured by pycnographic analysis of the product^9–11. In the absence of ATP⁶, synthesis appears to be of the repair type¹². In these systems, ATP does not merely protect the deoxynucleoside triphosphate pool^9,13 or stimulate the rec B, C nuclease⁶.