Structural basis of Fic-mediated adenylylation

Nat Struct Mol Biol. 2010 Aug;17(8):1004-10. doi: 10.1038/nsmb.1867. Epub 2010 Jul 11.


The Fic family of adenylyltransferases, defined by a core HPFx(D/E)GN(G/K)R motif, consists of over 2,700 proteins found in organisms from bacteria to humans. The immunoglobulin-binding protein A (IbpA) from the bacterial pathogen Histophilus somni contains two Fic domains that adenylylate the switch1 tyrosine residue of Rho-family GTPases, allowing the bacteria to subvert host defenses. Here we present the structure of the second Fic domain of IbpA (IbpAFic2) in complex with its substrate, Cdc42. IbpAFic2-bound Cdc42 mimics the GDI-bound state of Rho GTPases, with both its switch1 and switch2 regions gripped by IbpAFic2. Mutations disrupting the IbpAFic2-Cdc42 interface impair adenylylation and cytotoxicity. Notably, the switch1 tyrosine of Cdc42 is adenylylated in the structure, providing the first structural view for this post-translational modification. We also show that the nucleotide-binding mechanism is conserved among Fic proteins and propose a catalytic mechanism for this recently discovered family of enzymes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / metabolism*
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism*
  • Biocatalysis
  • Cell Death
  • Computer Simulation
  • Crystallography, X-Ray
  • Green Fluorescent Proteins / metabolism
  • Guanine Nucleotide Dissociation Inhibitors / metabolism
  • HeLa Cells
  • Humans
  • Models, Molecular
  • Mutant Proteins / chemistry
  • Mutant Proteins / metabolism
  • Nucleotides / metabolism
  • Protein Binding
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / metabolism
  • Structure-Activity Relationship
  • cdc42 GTP-Binding Protein / chemistry
  • cdc42 GTP-Binding Protein / metabolism


  • Bacterial Proteins
  • Guanine Nucleotide Dissociation Inhibitors
  • Mutant Proteins
  • Nucleotides
  • Recombinant Fusion Proteins
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins
  • cdc42 GTP-Binding Protein
  • Adenine

Associated data

  • PDB/3N3U
  • PDB/3N3V