Viral hijacking of a replicative helicase loader and its implications for helicase loading control and phage replication

Elife. 2016 May 31;5:e14158. doi: 10.7554/eLife.14158.


Replisome assembly requires the loading of replicative hexameric helicases onto origins by AAA+ ATPases. How loader activity is appropriately controlled remains unclear. Here, we use structural and biochemical analyses to establish how an antimicrobial phage protein interferes with the function of the Staphylococcus aureus replicative helicase loader, DnaI. The viral protein binds to the loader's AAA+ ATPase domain, allowing binding of the host replicative helicase but impeding loader self-assembly and ATPase activity. Close inspection of the complex highlights an unexpected locus for the binding of an interdomain linker element in DnaI/DnaC-family proteins. We find that the inhibitor protein is genetically coupled to a phage-encoded homolog of the bacterial helicase loader, which we show binds to the host helicase but not to the inhibitor itself. These findings establish a new approach by which viruses can hijack host replication processes and explain how loader activity is internally regulated to prevent aberrant auto-association.

Keywords: AAA+ ATPase; S. aureus; bacteriophage; biochemistry; biophysics; helicase; helicase loader; replication; structural biology; virus.

MeSH terms

  • Amino Acid Motifs
  • Anti-Bacterial Agents / chemistry
  • Anti-Bacterial Agents / metabolism
  • Antimicrobial Cationic Peptides / chemistry*
  • Antimicrobial Cationic Peptides / genetics
  • Antimicrobial Cationic Peptides / metabolism
  • Bacterial Proteins / antagonists & inhibitors
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Binding Sites
  • Cloning, Molecular
  • Crystallography, X-Ray
  • DNA Helicases / antagonists & inhibitors
  • DNA Helicases / chemistry*
  • DNA Helicases / genetics
  • DNA Helicases / metabolism
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Gene Expression
  • Models, Molecular
  • Protein Binding
  • Protein Conformation, alpha-Helical
  • Protein Conformation, beta-Strand
  • Protein Interaction Domains and Motifs
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Staphylococcus Phages / chemistry
  • Staphylococcus Phages / genetics*
  • Staphylococcus Phages / pathogenicity
  • Staphylococcus aureus / virology*
  • Thermodynamics
  • Viral Proteins / chemistry*
  • Viral Proteins / genetics
  • Viral Proteins / metabolism
  • Virus Replication*


  • Anti-Bacterial Agents
  • Antimicrobial Cationic Peptides
  • Bacterial Proteins
  • Recombinant Proteins
  • Viral Proteins
  • DNA Helicases