title: Positive selection scanning reveals decoupling of enzymatic activities of carbamoyl phosphate synthetase in Helicobacter pylori.
abstract: In an effort to detect factors which may be under positive selection, a survey for such genes in two pathogenic strains of Helicobacter pylori (J99 and 26695) was performed. Based on an analysis of synonymous and nonsynonymous substitutions, we identified 19 candidate genes under positive selection. A search for homologues with known crystallographic structures revealed Escherichia coli carbomoyl phosphate synthetase as a homologue of H. pylori carbamoyl phosphate synthetase. Carbamoyl phosphate synthetase as isolated from E. coli is a heterodimeric enzyme that possesses two different but coupled functionalities and is involved in the first committed step in the separate biosynthetic pathways for arginine and pyrimidine nucleotides. In this study, we provide evidence indicating that one of these functionalities appears to be under selective pressure. Reports from previously published site-directed mutagenesis studies point to a decoupling of amidotransferase and synthetase activities. Implications of these findings for a metabolic enzyme under positive selection are discussed in terms of the mechanisms of H. pylori pathogenesis.
authors.affiliation: Department of Biochemistry and Biophysics and Stockholm Bioinformatics Center, Stockholm University, 10691 Stockholm, Sweden.
authors.forename: Wagied
authors.initials: W
authors.lastname: Davids
authors.forename: Junaid
authors.initials: J
authors.lastname: Gamieldien
authors.forename: David A
authors.initials: DA
authors.lastname: Liberles
authors.forename: Winston
authors.initials: W
authors.lastname: Hide
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D019733:Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor / Q000235:genetics*; D019143:Evolution, Molecular; D016480:Helicobacter pylori / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D019733:Carbon-Nitrogen Ligases with Glutamine as Amide-N-Donor; C064716:carbamoyl phosphate synthetase (arginine-specific)