title: [Mutations in the purine nucleoside phosphorylase (pup) gene of Escherichia coli K-12 characterized by leaky damage to enzymatic activity and a pleiotropic effect].
abstract: The phenotype of earlier obtained mutants AIR38 and AIR6 is caused by leaky mutations of the structural gene for purine nucleoside phosphorylase (pup). These mutants are unable to grow on the medium with inosine as the only carbon source in the presence of thymidine. In contrast to ordinary leaky mutations, AIR38 and AIR6 are dominant in heterozygotes. When the strain F' with mutations AIR38 or AIR6 on episomes was used for conjugational matings with F- recA (pup+), recombinants with unexpected phenotype were observed: about 20% of recombinants F' became pup+ and thus the convertion of AIR38 and AIR6 alleles to pup+ took place. AIR38 mutation, unlike AIR6, is mapped in the proximal region of the pup gene and is characterized by pleyotropic effect on deo-genes: the inosine-induction of purine nucleoside phosphorylase in AIR38 mutant is absent and the induction of thymidine phosphorylase by exogenous thymidine is decreased. A speculation was made that the mutation AIR38 altered the structure of purine nucleoside phosphorylase in the site responsible for its interaction with membrane.
mesh_terms: D003227:Conjugation, Genetic; D004789:Enzyme Activation; D004790:Enzyme Induction; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005796:Genes; D005838:Genotype; D009154:Mutation; D009876:Operon; D010430:Pentosyltransferases / Q000235:genetics*; D010641:Phenotype; D010957:Plasmids; D011683:Purine-Nucleoside Phosphorylase / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D010430:Pentosyltransferases; D011683:Purine-Nucleoside Phosphorylase
vernacular_title: Mutatsii po purinnukleozidfosforilaznomu (pup) genu Escherichia coli K-12, kharakterizuiushchiesia nepolnym povrezhdeniem aktivnosti fermenta i pleĭotropnym éffektom.