Bacteriophage P22 tail accessory factor GP26 is a long triple-stranded coiled-coil

J Biol Chem. 2005 Feb 18;280(7):5929-33. doi: 10.1074/jbc.C400513200. Epub 2004 Dec 8.


P22 is a well characterized tailed bacteriophage that infects Salmonella enterica serovar Typhimurium. It is characterized by a "short" tail, which is formed by five proteins: the dodecameric portal protein (gp1), three tail accessory factors (gp4, gp10, gp26), and six trimeric copies of the tail-spike protein (gp9). We have isolated the gene encoding tail accessory factor gp26, which is responsible for stabilization of viral DNA within the mature phage, and using a variety of biochemical and biophysical techniques we show that gp26 is very likely a triple stranded coiled-coil protein. Electron microscopic examination of purified gp26 indicates that the protein adopts a rod-like structure approximately 210 angstroms in length. This trimeric rod displays an exceedingly high intrinsic thermostability (T(m) approximately 85 degrees C), which suggests a potentially important structural role within the phage tail apparatus. We propose that gp26 forms the thin needle-like fiber emanating from the base of the P22 neck that has been observed by electron microscopy of negatively stained P22 virions. By analogy with viral trimeric coiled-coil class I membrane fusion proteins, gp26 may represent the membrane-penetrating device used by the phage to pierce the host outer membrane.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Bacteriophage P22 / chemistry*
  • Bacteriophage P22 / ultrastructure
  • Computational Biology
  • Microscopy, Electron
  • Molecular Sequence Data
  • Protein Structure, Secondary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / ultrastructure
  • Viral Tail Proteins / chemistry*
  • Viral Tail Proteins / genetics
  • Viral Tail Proteins / isolation & purification
  • Viral Tail Proteins / ultrastructure


  • Recombinant Proteins
  • Viral Tail Proteins