Heterotropic interactions in aspartate transcarbamoylase: Turning allosteric ATP activation into inhibition as a consequence of a single tyrosine to phenylalanine mutation Academic Article uri icon


MeSH Major

  • Adenosine Triphosphate
  • Aspartate Carbamoyltransferase
  • Escherichia coli
  • Mutagenesis, Site-Directed
  • Phenylalanine
  • Tyrosine


  • Aspartate transcarbamoylase (EC is extensively studied as a model for cooperativity and allostery. This enzyme shows cooperativity between the catalytic sites, and its activity is feedback inhibited by CTP and activated by ATP. These regulatory processes involve several interfaces between catalytic and regulatory chains as well as between domains within these two types of chains. As far as the regulatory chain is concerned, its two domains are in contact through a hydrophobic interface, in which a tyrosine residue is inserted in a pocket involving two leucine residues of the allosteric domain and a valine and a leucine residue of the zinc domain. To probe the possible implication of this hydrophobic core in the CTP and ATP regulatory effect, the tyrosine was replaced by a phenylalanine through oligonucleotide-directed mutagenesis. Interestingly, the resulting mutant shows a complete inversion of the ATP effect; it is now inhibited by ATP instead of being activated by this nucleotide triphosphate. This mutant remains normally sensitive to the feedback inhibitor CTP. This result shows that the hydrophobic interface between the two domains of the regulatory chain plays an important role in the discrimination between the regulatory signals promoted by the two allosteric effectors.

publication date

  • October 15, 1991



  • Academic Article



  • eng

PubMed Central ID

  • PMC52676

PubMed ID

  • 1924381

Additional Document Info

start page

  • 9180

end page

  • 3


  • 88


  • 20