The helicase-binding domain of Escherichia coli DnaG primase interacts with the highly conserved C-terminal region of single-stranded DNA-binding protein.
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Naue N, Beerbaum M, Bogutzki A, Schmieder P, Curth U
The helicase-binding domain of Escherichia coli DnaG primase interacts with the highly conserved C-terminal region of single-stranded DNA-binding protein.
Nucleic Acids Res. 2013 Apr;41(8):4507-17. doi: 10.1093/nar/gkt107. Epub 2013 Feb 20.
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- 23430154 [ View in PubMed]
- Abstract
During bacterial DNA replication, DnaG primase and the chi subunit of DNA polymerase III compete for binding to single-stranded DNA-binding protein (SSB), thus facilitating the switch between priming and elongation. SSB proteins play an essential role in DNA metabolism by protecting single-stranded DNA and by mediating several important protein-protein interactions. Although an interaction of SSB with primase has been previously reported, it was unclear which domains of the two proteins are involved. This study identifies the C-terminal helicase-binding domain of DnaG primase (DnaG-C) and the highly conserved C-terminal region of SSB as interaction sites. By ConSurf analysis, it can be shown that an array of conserved amino acids on DnaG-C forms a hydrophobic pocket surrounded by basic residues, reminiscent of known SSB-binding sites on other proteins. Using protein-protein cross-linking, site-directed mutagenesis, analytical ultracentrifugation and nuclear magnetic resonance spectroscopy, we demonstrate that these conserved amino acid residues are involved in the interaction with SSB. Even though the C-terminal domain of DnaG primase also participates in the interaction with DnaB helicase, the respective binding sites on the surface of DnaG-C do not overlap, as SSB binds to the N-terminal subdomain, whereas DnaB interacts with the ultimate C-terminus.