Crystal structure of N-acetylornithine transcarbamylase from Xanthomonas campestris: a novel enzyme in a new arginine biosynthetic pathway found in several eubacteria

J Biol Chem. 2005 Apr 15;280(15):14366-9. doi: 10.1074/jbc.C500005200. Epub 2005 Feb 24.


We have identified in Xanthomonas campestris a novel N-acetylornithine transcarbamylase that replaces ornithine transcarbamylase in the canonic arginine biosynthetic pathway of several Eubacteria. The crystal structures of the protein in the presence and absence of the reaction product, N-acetylcitrulline, were determined. This new family of transcarbamylases lacks the DxxSMG motif that is characteristic of all ornithine transcarbamylases (OTCases) and contains a novel proline-rich loop that forms part of the active site. The specificity for N-acetylornithine is conferred by hydrogen bonding with residues in the proline-rich loop via water molecules and by hydrophobic interactions with residues from the adjacent 80's, 120's, and proline-rich loops. This novel protein structure provides a starting point for rational design of specific analogs that may be useful in combating human and plant pathogens that utilize acetylornithine transcarbamylase rather than ornithine transcarbamylase.

Publication types

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

MeSH terms

  • Binding Sites
  • Carboxyl and Carbamoyl Transferases / chemistry*
  • Cloning, Molecular
  • Crystallography, X-Ray
  • Ligands
  • Models, Molecular
  • Ornithine Carbamoyltransferase / chemistry*
  • Proline / chemistry
  • Protein Conformation
  • Protein Structure, Secondary
  • Water / chemistry
  • Xanthomonas campestris / enzymology*


  • Ligands
  • Water
  • Proline
  • Carboxyl and Carbamoyl Transferases
  • N-acetylornithine transcarbamylase
  • Ornithine Carbamoyltransferase

Associated data

  • PDB/1C9Y
  • PDB/1EKX
  • PDB/1JS1
  • PDB/1YH0
  • PDB/1YH1