Crystal structure of the VgrG1 actin cross-linking domain of the Vibrio cholerae type VI secretion system

J Biol Chem. 2012 Nov 2;287(45):38190-9. doi: 10.1074/jbc.M112.390153. Epub 2012 Aug 16.


Vibrio cholerae is the cause of the diarrheal disease cholera. V. cholerae produces RtxA, a large toxin of the MARTX family, which is targeted to the host cell cytosol, where its actin cross-linking domain (ACD) cross-links G-actin, leading to F-actin depolymerization, cytoskeleton rearrangements, and cell rounding. These effects on the cytoskeleton prevent phagocytosis and bacterial engulfment by macrophages, thus preventing V. cholerae clearance from the gut. The V. cholerae Type VI secretion-associated VgrG1 protein also contains a C-terminal ACD, which shares 61% identity with MARTX ACD and has been shown to covalently cross-link G-actin. Here, we purified the VgrG1 C-terminal domain and determined its crystal structure. The VgrG1 ACD exhibits a V-shaped three-dimensional structure, formed of 12 β-strands and nine α-helices. Its active site comprises five residues that are conserved in MARTX ACD toxin, within a conserved area of ∼10 Å radius. We showed that less than 100 ACD molecules are sufficient to depolymerize the actin filaments of a fibroblast cell in vivo. Mutagenesis studies confirmed that Glu-16 is critical for the F-actin depolymerization function. Co-crystals with divalent cations and ATP reveal the molecular mechanism of the MARTX/VgrG toxins and offer perspectives for their possible inhibition.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / chemistry
  • Actins / metabolism
  • Adenosine Diphosphate / chemistry
  • Adenosine Diphosphate / metabolism
  • Adenosine Triphosphate / chemistry
  • Adenosine Triphosphate / metabolism
  • Animals
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Binding Sites / genetics
  • Blotting, Western
  • Cell Line
  • Crystallography, X-Ray
  • Glutamic Acid / chemistry
  • Glutamic Acid / genetics
  • Glutamic Acid / metabolism
  • Humans
  • Magnesium / chemistry
  • Magnesium / metabolism
  • Manganese / chemistry
  • Manganese / metabolism
  • Models, Molecular
  • Mutation
  • Protein Binding
  • Protein Structure, Tertiary*
  • Rabbits
  • Vibrio cholerae / genetics
  • Vibrio cholerae / metabolism*


  • Actins
  • Bacterial Proteins
  • Glutamic Acid
  • Manganese
  • Adenosine Diphosphate
  • Adenosine Triphosphate
  • Magnesium

Associated data

  • PDB/4DTD
  • PDB/4DTF
  • PDB/4DTH
  • PDB/4DTL
  • PDB/4E1C
  • PDB/4E1D
  • PDB/4E1F