title: Isolation and characterization of a new temperature-sensitive polynucleotide phosphorylase mutation in Escherichia coli K-12.
abstract: Polynucleotide phosphorylase (PNPase) has been studied in detail since its discovery in 1955 [1]. In an attempt to determine what role, if any, it has in mRNA decay in Escherichia coli, we have isolated and characterized a temperature-sensitive mutation, pnp-200, in the pnp gene. In vitro phosphorolysis, polymerization and exchange activities of the partially purified Pnp-200 enzyme are all reduced to 30-40% of wild-type activity at 50 degrees C compared to 32 degrees C. The pnp-200 mutation alone does not affect cell growth or mRNA stability. A triple mutant strain containing pnp-200 in combination with other temperature-sensitive mutations in genes known to affect mRNA metabolism (rnb-500 and ams-1) is conditionally lethal and shows increased mRNA stability after shift to the non-permissive temperature.
authors.affiliation: Department of Genetics, University of Georgia, Athens 30602.
authors.forename: S D
authors.initials: SD
authors.lastname: Yancey
authors.forename: S R
authors.initials: SR
authors.lastname: Kushner
mesh_terms: D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005798:Genes, Bacterial; D005838:Genotype; D006358:Hot Temperature; D007700:Kinetics; D009154:Mutation; D010957:Plasmids; D011117:Polyribonucleotide Nucleotidyltransferase / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D013816:Thermodynamics
chemical_list: D011117:Polyribonucleotide Nucleotidyltransferase