Transcriptional regulation of Escherichia coli K-12 major outer membrane protein 1b

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Abstract
Eleven independent insertion mutations were isolated that prevented expression of major outer membrane protein 1b. Of the mutations, 7 were Mucts insertions located at ompB. These ompB::Mucts strains fell into 2 phenotypic classes with regard to expression of proteins 1a and 1b. The remaining 4 mutants were comprised of 1 Tn5 and 3 Mucts insertions mapping at par. The Mucts insertions at par were used to construct fusions of the lac operon to the par promoter. Expression of .beta.-galactosidase in these fusion strains reflected known regulatory properties of protein 1b. When an ompB allele was introduced into the par-lac fusion strains, .beta.-galactosidase activity was reduced 14- to 31-fold. Transcriptional regulation of the par gene and the existence of 2 functions at ompB are discussed. Par may be the structural gene for protein 1b. An ompB gene product may be a diffusible, positive regulatory element controlling expression of par.