Allosteric regulation of the primase (DnaG) activity by the clamp-loader (τ) in vitro

Kiran Chintakayala, Cristina MacHón, Anna Haroniti, Marilyn A. Larson, Steven H. Hinrichs, Mark A. Griep, Panos Soultanas

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


During DNA replication the helicase (DnaB) recruits the primase (DnaG) in the replisome to initiate the polymerization of new DNA strands. DnaB is attached to the τ subunit of the clamp-loader that loads the β clamp and interconnects the core polymerases on the leading and lagging strands. The τ-DnaB-DnaG ternary complex is at the heart of the replisome and its function is likely to be modulated by a complex network of allosteric interactions. Using a stable ternary complex comprising the primase and helicase from Geobacillus stearothermophilus and the τ subunit of the clamp-loader from Bacillus subtilis we show that changes in the DnaB-τ interaction can stimulate allosterically primer synthesis by DnaG in vitro. The A550V τ mutant stimulates the primase activity more efficiently than the native protein. Truncation of the last 18 C-terminal residues of τ elicits a DnaG-stimulatory effect in vitro that appears to be suppressed in the native τ protein. Thus changes in the τ-DnaB interaction allosterically affect primer synthesis. Although these C-terminal residues of τ are not involved directly in the interaction with DnaB, they may act as a functional gateway for regulation of primer synthesis by τ-interacting components of the replisome through the τ-DnaB-DnaG pathway.

Original languageEnglish (US)
Pages (from-to)537-549
Number of pages13
JournalMolecular Microbiology
Issue number2
StatePublished - Apr 2009

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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