The hexameric structure of a conjugative VirB4 protein ATPase provides new insights for a functional and phylogenetic relationship with DNA translocases

J Biol Chem. 2012 Nov 16;287(47):39925-32. doi: 10.1074/jbc.M112.413849. Epub 2012 Oct 3.

Abstract

VirB4 proteins are ATPases essential for pilus biogenesis and protein transport in type IV secretion systems. These proteins contain a motor domain that shares structural similarities with the motor domains of DNA translocases, such as the VirD4/TrwB conjugative coupling proteins and the chromosome segregation pump FtsK. Here, we report the three-dimensional structure of full-length TrwK, the VirB4 homologue in the conjugative plasmid R388, determined by single-particle electron microscopy. The structure consists of a hexameric double ring with a barrel-shaped structure. The C-terminal half of VirB4 proteins shares a striking structural similarity with the DNA translocase TrwB. Docking the atomic coordinates of the crystal structures of TrwB and FtsK into the EM map revealed a better fit for FtsK. Interestingly, we have found that like TrwB, TrwK is able to bind DNA with a higher affinity for G4 quadruplex structures than for single-stranded DNA. Furthermore, TrwK exerts a dominant negative effect on the ATPase activity of TrwB, which reflects an interaction between the two proteins. Our studies provide new insights into the structure-function relationship and the evolution of these DNA and protein translocases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / chemistry*
  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism
  • Agrobacterium tumefaciens / enzymology*
  • Agrobacterium tumefaciens / genetics
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Carrier Proteins / chemistry*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Crystallography, X-Ray
  • DNA, Single-Stranded / chemistry*
  • DNA, Single-Stranded / genetics
  • DNA, Single-Stranded / metabolism
  • Fimbriae, Bacterial / chemistry
  • Fimbriae, Bacterial / genetics
  • Fimbriae, Bacterial / metabolism
  • Molecular Docking Simulation*
  • Phylogeny*
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary
  • Structure-Activity Relationship

Substances

  • Bacterial Proteins
  • Carrier Proteins
  • DNA, Single-Stranded
  • Adenosine Triphosphatases