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Updated: Jul 16, 2026

Production of Xenopus tropicalis Egg Extracts to Identify Microtubule-associated RNAs
Published on: June 27, 2013
Sequence, expression and evolutionary relationships of carbamoyl phosphate synthetase I in the toad Xenopus laevis
Timothy E Lindley1, Tammy Laberge, Aaron Hall
1Department of Biochemistry and Molecular Biology, University of Minnesota-Duluth, Duluth, Minnesota 55812-2487, USA.
Abstract:
The sequence of carbamoyl phosphate synthetase I (CPSase I) cDNA and expression of the enzyme in liver of the toad Xenopus laevis are reported. CPSase I mRNA increases 6-fold when toads are exposed to high salinity for extended periods of time. The deduced 1,494-amino acid sequence of the CPSase I is homologous to other CPSases and reveals a domain structure and conserved amino acids common to other CPSases. A serine residue (S287) is present where there is a cysteine residue required for glutamine-dependent activity in CPSase Types III and II (Type I CPSases utilize only ammonia as nitrogen-donating substrate). A sequence of DNA 964 bases upstream from the ATG start codon for the CPSase I gene is also reported. Phylogenetic analysis for 30 CPSase isoforms, including X. laevis CPSase I, across a wide spectrum of phyla is reported and discussed. The results are consistent with the views that eukaryotic CPSase II as a multifunctional complex evolved from prokaryotic CPSase II and that CPSase I in terrestrial vertebrates and CPSase III in fishes arose from eukaryotic CPSase II by independent events after the divergence of plants in eukaryotic evolution.
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