Triggering of Allostery in an Enzyme by a Point Mutation: Ornithine Transcarbamoylase
- 4 August 1989
- journal article
- research article
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 245 (4917), 522-524
- https://doi.org/10.1126/science.2667139
Abstract
The origin of allostery is an unanswered question in the evolution of complex regulatory proteins. Anabolic ornithine transcarbamoylase, a trimer of identical subunits, is not an allosteric enzyme per se. However, when the active-site residue arginine-106 of the Escherichia coli enzyme is replaced with a glycine through site-directed mutagenesis, the resultant mutant enzyme manifests substrate cooperativity that is absent in the wild-type enzyme. Both homotropic and heterotropic interactions occur in the mutant enzyme. The initial velocity saturation curves of the substrates, carbamoyl phosphate and L-ornithine, conform to the Hill equation. The observed cooperativity depends on substrate but not enzyme concentration. The finding underscores the possibility that a single mutation of the enzyme in the cell could turn transcarbamoylation into a regulatory junction in the biosynthesis of L-arginine and urea.This publication has 20 references indexed in Scilit:
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