title: A mutation affecting the regulation of a secA-lacZ fusion defines a new sec gene.
abstract: It was shown previously that the secA gene of Escherichia coli is derepressed in cells that have a defect in protein export. Here it is demonstrated that the beta-galactosidase produced by a secA-lacZ gene fusion strain is regulated in the same way. Studies on the fusion strain reveal that the promoter or a site involved in regulation of the secA gene is located considerably upstream from the structural gene. The properties of the fusion strain provide a new selection for mutants that are defective in protein export. Selection for increased lac expression of a secA-lacZ fusion strain yields mutations in three of the known sec genes, secA, secD and prlA/secY. In addition, mutations in several genes not previously known to affect secA expression were obtained. A mutation in one of these genes causes a pleiotropic defect in protein export and a cold-sensitive growth defect; this gene, which maps at approximately 90 min on the bacterial chromosome, has been named secE.
authors.affiliation: Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: P D
authors.initials: PD
authors.lastname: Riggs
authors.forename: A I
authors.initials: AI
authors.lastname: Derman
authors.forename: J
authors.initials: J
authors.lastname: Beckwith
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D007763:Lac Operon; D009154:Mutation
chemical_list: D001426:Bacterial Proteins