Insertion and spontaneous mutants defective in the production of the major outer membrane protein, OmpF§ § Abbreviations used: Several nomenclature systems have been used for the major outer membrane proteins of Escherichia coli. To avoid confusion, we give the protein the same name as the structural gene. For example, the ompF gene specifies the OmpF protein. Certain ompB alleles, isolated in different laboratories, have been given different names. The ompB allele that confers an OmpF- OmpC+ phenotype has also been called tpo (Wandersman et al., 1980) and perA (Wanner et al., 1979). Genetic nomenclature is from Bachmann & Low (1980). The symbol Φ designates fusions (Muller-Hill & Kania, 1974; Silhavy et al., 1976), which may be of two types: those that result in production of a hybrid protein caused by fusion of two structural genes (protein fusions) and those that do not result in the production of a hybrid protein (operon fusions) (see Fig. 1), but only place a gene under the regulatory control of a different promoter. Protein fusions and operon fusions are designated as Φ(ompF-lacZ)hyb and Φ(ompF-lacZ+), respectively. Fusion components are written in their order of transcription. The superscript c, as in ompCc, indicates a mutation causing constitutive expression of the gene. Bacteriophage λ nomenclature is from Hershey (1971). Primes, as in ompF′, indicate that the DNA for the genetic region referred to is deleted on the side the prime is written. The symbol::, as in ompF::Tn5, indicates the site of a genetic insertion. Tn5 is a translocon conferring kanamycin resistance (Berg, 1977). The symbol Δ indicates a deletion. Phenotype abbreviations are Lac, lactose; Kan, kanamycin; s, sensitive; r, resistant; Ts, temperature-sensitive. Other abbreviations are: NB, nutrient broth; TY broth, Tryptone yeast extract broth; TSB, tryptic soy broth; XG, 5-bromo-4-chloro-3-indolyl-β-d-galactoside., were selected by tolerance to colicin L. Eight of the insertion mutations were insertions of the genome of bacteriophage Mu at ompF. One insertion was the kanamycin resistance translocon Tn5, also in ompF. The Muc(Ts) insertions at ompF were used to construct both ompF-lac operon and protein fusions. These fusions and ompC-lac fusions isolated previously (Hall & Silhavy, 1979) enabled us to study the regulatory properties of the ompF and ompC genes and to further clarify the role of the ompB locus. The results indicate that the ompB locus performs the dual role of regulating both the absolute and relative transcriptional levels of expression of the ompF and ompC genes.
All Science Journal Classification (ASJC) codes
- Structural Biology
- Molecular Biology