An isolated Hda-clamp complex is functional in the regulatory inactivation of DnaA and DNA replication

Hironori Kawakami, Masayuki Su'etsugu, Tsutomu Katayama

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

In Escherichia coli, a complex consisting of Hda and the DNA-loaded clamp-subunit of the DNA polymerase III holoenzyme promotes hydrolysis of DnaA-ATP. The resultant ADP-DnaA is inactive for initiation of chromosomal DNA replication, thereby repressing excessive initiations. As the cellular content of the clamp is 10-100 times higher than that of Hda, most Hda molecules might be complexed with the clamp in vivo. Although Hda predominantly forms irregular aggregates when overexpressed, in the present study we found that co-overexpression of the clamp with Hda enhances Hda solubility dramatically and we efficiently isolated the Hda-clamp complex. A single molecule of the complex appears to consist of two Hda molecules and a single clamp. The complex is competent in DnaA-ATP hydrolysis and DNA replication in the presence of DNA and the clamp deficient subassembly of the DNA polymerase III holoenzyme (pol III*). These findings indicate that the clamp contained in the complex is loaded onto DNA through an interaction with the pol III* and that the Hda activity is preserved in these processes. The complex consisting of Hda and the DNA-unloaded clamp may play a specific role in a process proceeding to the DnaA-ATP hydrolysis in vivo.

Original languageEnglish
Pages (from-to)220-229
Number of pages10
JournalJournal of structural biology
Volume156
Issue number1
DOIs
Publication statusPublished - Oct 1 2006

All Science Journal Classification (ASJC) codes

  • Structural Biology

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