title: Conditionally lethal amber mutations in the leader peptidase gene of Escherichia coli.
abstract: The lep gene of Escherichia coli encodes the leader peptidase which cleaves amino-terminal leader sequences of secreted proteins. To facilitate the study of structure-function relationships of the leader peptidase, 22 amber mutations in lep were isolated by localized mutagenesis. These amber mutants grew at 32 degrees C but not at 42 degrees C in the presence of a temperature-sensitive amber suppressor. Most of them were lethal under sup0 conditions. However, one amber mutant, the lep-9 mutant, exhibited temperature-sensitive growth in the sup0 strain, indicating that the amber fragment is active at 32 degrees C but not at 42 degrees C. Protein precursors of the maltose-binding protein and OmpA accumulate strikingly in the lep-9 mutant.
authors.affiliation: Department of Tumor Biology, University of Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Inada
authors.forename: D L
authors.initials: DL
authors.lastname: Court
authors.forename: K
authors.initials: K
authors.lastname: Ito
authors.forename: Y
authors.initials: Y
authors.lastname: Nakamura
mesh_terms: D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D010450:Endopeptidases / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D005796:Genes; D005798:Genes, Bacterial; D005804:Genes, Lethal; D008565:Membrane Proteins; D009154:Mutation; D010957:Plasmids; D015183:Restriction Mapping; D012697:Serine Endopeptidases; D014161:Transduction, Genetic
chemical_list: D008565:Membrane Proteins; D010450:Endopeptidases; D012697:Serine Endopeptidases; C026515:type I signal peptidase