Fusion of the lac Genes to the Proximal Promoters of the deo Operon of Escherichia coli K12

Abstract

241Fusions of the ldC structural genes to the proximal promoters deoP and cytP of the deo operon have been isolated using a h (lac, Mu') phage. This phage was inserted into a heatinducible Mu prophage which had itself been inserted into the deoA gene. Selection was made for heat-resistant derivatives of this lysogen which maximally expressed the lac genes when an inducer of the deo operon was present; these were shown to have the lac genes fused to the deo operon-in some cases with a concomitant deletion of the deoC gene, whilst in others deoC was retained. The level of P-galactosidase activity in these strains was induced by growth in the presence of deoxyadenosine or cytidine, both of which lead to induction of the deo enzymes -deoxyadenosine through the deoOP system and cytidine through the cytOP system. The level of induction of P-galactosidase was of the same order as the level of induction of deoxyriboaldolase, the deoC gene product, in those strains retaining an intact deoC+ gene. Plaque-forming h phages carrying the deo-lac fusions were isolated by inducing the lysogens with mitomycin C.

deoP1 promoter and operator mutants in Escherichia coli: isolation and characterization

“…S03128 (F^, was a gift from Dr. R.S. Buxton (Buxton, 1979). The other strains used in this work have been described previously (Dandanell and Hammer, 1985).…”

“…In . the lacZ expression is under conXro\ of DeoR (Buxton, 1979) and differences in titration efficiency can be visualized by monitoring the phenotypes on MacConkey lactose plates. Cells {S03128) containing pKO500 grow as white colonies whereas ceiis containing pGD11 or pGD12 grow as red colonies.…”

Identification and characterization of genes (xapA, xapB, and xapR) involved in xanthosine catabolism in Escherichia coli

“…Several xap mutants have previously been characterized, but these were mainly regulatory xapR mutants that were affected in inducer binding so that other nucleosides could substitute for xanthosine (7,20,21). We therefore mutated each of the xap genes (Table 3).…”