Location of the serine residue involved in the linkage between the terminal protein and the DNA of phage phi 29

Nucleic Acids Res. 1985 Nov 11;13(21):7715-28. doi: 10.1093/nar/13.21.7715.


B. subtilis phage phi 29 has a terminal protein, p3, covalently linked to the 5' ends of the DNA through a phosphodiester bond between a serine residue and 5'-dAMP. This protein acts as a primer in DNA replication by forming an initiation complex with the 5'-terminal nucleotide dAMP. The amino acid sequence of the terminal protein, deduced from the nucleotide sequence of gene 3, showed the presence of 18 serine residues in a total of 266 amino acids. In this paper we have identified the serine involved in the linkage with the DNA as the residue 232, located close to the C-terminus of the molecule. This result was obtained by amino acid analysis of the peptide that remains linked to the DNA after proteinase K digestion of the terminal protein-phi 29 DNA complex and automated Edman degradation of the corresponding [125I]-labeled tryptic peptide. Prediction of the secondary structure of the terminal protein suggested that the serine residue involved in the linkage with the DNA is placed in a beta-turn, probably located on the external part of the molecule, as indicated by hydropathic values.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Bacillus subtilis / genetics*
  • Bacteriophages / genetics*
  • Binding Sites
  • DNA, Viral / metabolism*
  • DNA-Binding Proteins / metabolism*
  • Iodine Radioisotopes
  • Peptide Fragments / analysis
  • Protein Binding
  • Serine*
  • Trypsin
  • Viral Proteins / metabolism*


  • DNA, Viral
  • DNA-Binding Proteins
  • Iodine Radioisotopes
  • Peptide Fragments
  • Viral Proteins
  • Serine
  • Trypsin