New insights in the ϕ29 terminal protein DNA-binding and host nucleoid localization functions

Mol Microbiol. 2014 Jan;91(2):232-41. doi: 10.1111/mmi.12456. Epub 2013 Nov 27.


Protein-primed DNA replication constitutes a strategy to initiate viral DNA synthesis in a variety of prokaryotic and eukaryotic organisms. Although the main function of viral terminal proteins (TPs) is to provide a free hydroxyl group to start initiation of DNA replication, there are compelling evidences that TPs can also play other biological roles. In the case of Bacillus subtilis bacteriophage ϕ29, the N-terminal domain of the TP organizes viral DNA replication at the bacterial nucleoid being essential for an efficient phage DNA replication, and it contains a nuclear localization signal (NLS) that is functional in eukaryotes. Here we provide information about the structural properties of the ϕ29 TP N-terminal domain, which possesses sequence-independent DNA-binding capacity, and dissect the amino acid residues important for its biological function. By mutating all the basic residues of the TP N-terminal domain we identify the amino acids responsible for its interaction with the B. subtilis genome, establishing a correlation between the capacity of DNA-binding and nucleoid localization of the protein. Significantly, these residues are important to recruit the DNA polymerase at the bacterial nucleoid and, subsequently, for an efficient phage DNA replication.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus Phages / genetics
  • Bacillus Phages / metabolism*
  • Bacillus subtilis / genetics
  • Bacillus subtilis / metabolism
  • Bacillus subtilis / virology*
  • Binding Sites
  • Cell Nucleus / metabolism
  • Circular Dichroism
  • DNA Replication*
  • DNA, Bacterial / metabolism*
  • DNA, Viral / genetics
  • DNA, Viral / metabolism*
  • DNA-Directed DNA Polymerase / metabolism
  • Models, Molecular
  • Nuclear Localization Signals / metabolism*
  • Protein Conformation
  • Protein Structure, Secondary
  • Sequence Alignment
  • Viral Proteins / chemistry
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*


  • DNA, Bacterial
  • DNA, Viral
  • Nuclear Localization Signals
  • Viral Proteins
  • terminal protein, Bacillus phage phi29
  • DNA-Directed DNA Polymerase