The structure and assembly mechanism of a novel three-stranded tubulin filament that centers phage DNA

Structure. 2014 Apr 8;22(4):539-48. doi: 10.1016/j.str.2014.02.006. Epub 2014 Mar 13.


Tubulins are a universally conserved protein superfamily that carry out diverse biological roles by assembling filaments with very different architectures. The underlying basis of this structural diversity is poorly understood. Here, we determine a 7.1 Å cryo-electron microscopy reconstruction of the bacteriophage-encoded PhuZ filament and provide molecular-level insight into its cooperative assembly mechanism. The PhuZ family of tubulins is required to actively center the phage within infected host cells, facilitating efficient phage replication. Our reconstruction and derived model reveal the first example of a three-stranded tubulin filament. We show that the elongated C-terminal tail simultaneously stabilizes both longitudinal and lateral interactions, which in turn define filament architecture. Identified interaction surfaces are conserved within the PhuZ family, and their mutagenesis compromises polymerization in vitro and in vivo. Combining kinetic modeling of PhuZ filament assembly and structural data, we suggest a common filament structure and assembly mechanism for the PhuZ family of tubulins.

MeSH terms

  • Cryoelectron Microscopy
  • DNA, Viral / chemistry*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Gene Expression
  • Models, Molecular
  • Promoter Regions, Genetic
  • Protein Binding
  • Protein Multimerization
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Pseudomonas / virology
  • Pseudomonas Phages / chemistry*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Tubulin / chemistry*
  • Tubulin / genetics
  • Viral Proteins / chemistry*
  • Viral Proteins / genetics


  • DNA, Viral
  • Recombinant Proteins
  • Tubulin
  • Viral Proteins

Associated data

  • PDB/3J5V