Role of the amino-terminal region of the DnaA protein in opening of the duplex DNA at the oriC region

We report in this paper that the amino acid residues Ile-26 and Leu-40 of t he DnaA protein are essential for the DNA replication activity in vitro. Li nes of evidence to support this conclusion are as follows. Variants of the DnaA protein containing either an Ile-26-Ser or Leu-40-Ser replacement were unable to support oriC DNA replication in vitro. Though the mutant DnaA pr oteins retained the capability to bind oriC DNA, they were unable to open t he duplex DNA at oriC. Based on these and other results, we conclude that t he N-terminal region of the DnaA protein is involved in the oligomerization of this protein, an essential step for the duplex opening activity at oriC , (C) 1999 Federation of European Microbiological Societies. Published by E lsevier Science B.V. All rights reserved.