title: Genomic hsd-Mu(lac) operon fusion mutants of Escherichia coli K-12.
abstract: Genomic (chromosomal)hsd-Mu(lac) operon fusions have been constructed in two strains of Escherichia coli K-12 for the three hsd genes, hsdRK, hsdMK and hsdSK, using MudX and lambda placMu53. Expression of hsdK mutants ranged from 16 to 74 units (u) (with a mean of 52 u) for fusions to promoter pres and ranged from 26-75 u (also with a mean of 52 u) for fusions to promoter pmod. The expression of the two hsdK promoters was measured in different stages of growth. The pres fusion mutant showed a lag in beta-galactosidase (beta Gal) production, as compared to the pmod fusion mutant. One r-Km-K mutant (JR205) showed more than ten times the beta Gal activity of other insertion mutants. The activity of this mutant decreased by 20-fold upon the transfer of F101-102, which includes the wild-type hsd region. Positive gene-dosage effect was observed using F' plasmids containing the hsd-lacZ region.
authors.affiliation: Department of Microbiology, School of Medicine, Loma Linda University, CA 92350.
authors.forename: A
authors.initials: A
authors.lastname: Prakash
authors.forename: B
authors.initials: B
authors.lastname: Valinluck
authors.forename: J
authors.initials: J
authors.lastname: Ryu
mesh_terms: D010583:Bacteriophage mu / Q000235:genetics*; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D005144:F Factor; D005798:Genes, Bacterial; D007763:Lac Operon; D016296:Mutagenesis; D010641:Phenotype; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping