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Publication Abstract from PubMed

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.

Crystal structure of N-acetylornithine transcarbamylase from Xanthomonas campestris: a novel enzyme in a new arginine biosynthetic pathway found in several eubacteria.,Shi D, Morizono H, Yu X, Roth L, Caldovic L, Allewell NM, Malamy MH, Tuchman M J Biol Chem. 2005 Apr 15;280(15):14366-9. Epub 2005 Feb 24. PMID:15731101^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.