Overproduction and purification of protein P6 of Bacillus subtilis phage phi 29: role in the initiation of DNA replication

Nucleic Acids Res. 1985 May 10;13(9):3083-100. doi: 10.1093/nar/13.9.3083.


A phi 29 DNA fragment containing gene 6, required for DNA replication, has been cloned in plasmid pPLc28 under the control of the PL promoter of phage lambda. A polypeptide with an electrophoretic mobility close to that of p6 was labelled with 35S-methionine after heat induction. This protein, representing about 4% of the total E. coli protein after 1 h of induction, was obtained in a highly purified form. The protein was characterized as p6 by amino acid analysis and NH2-and COOH-terminal sequence determination. Protein p6 has an apparent molecular weight of 23,600, suggesting that the native form of the protein is a dimer. The purified protein p6 stimulated the protein-primed initiation of phi 29 DNA replication when added to purified proteins p2 (phi 29-coded DNA polymerase) and p3 (terminal protein).

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Amino Acids / analysis
  • Bacillus subtilis
  • Bacteriophage lambda / genetics
  • Bacteriophages / genetics*
  • DNA Replication*
  • Electrophoresis, Polyacrylamide Gel
  • Molecular Weight
  • Operon
  • Plasmids
  • Ultracentrifugation
  • Viral Proteins / isolation & purification*


  • Amino Acids
  • Viral Proteins