crpX mutants of Escherichia coli K12: Specific regulatory effects of altered cyclic AMP receptor proteins

1982 ◽  
Vol 187 (2) ◽  
pp. 291-296 ◽  
Author(s):  
Nicole Guiso ◽  
Evelyne Joseph ◽  
Jacques Daniel
Keyword(s):  
Escherichia Coli ◽  
Cyclic Amp ◽  
Receptor Proteins ◽  
Escherichia Coli K12 ◽  
Regulatory Effects

scholarly journals CRYPTIC OPERON FOR β-GLUCOSIDE METABOLISM IN ESCHERICHIA COLI K12: GENETIC EVIDENCE FOR A REGULATORY PROTEIN

Genetics ◽  
1981 ◽  
Vol 97 (1) ◽  
pp. 11-25
Author(s):  
Roberto Defez ◽  
Maurilio De Felice
Keyword(s):  
Escherichia Coli ◽  
Cyclic Amp ◽  
Single Gene ◽  
Regulatory Protein ◽  
Regulatory Site ◽  
Structural Genes ◽  
Wild Type ◽  
Cis Acting ◽  
E Coli ◽  
Escherichia Coli K12

ABSTRACT Escherichia coli K12 does not metabolize β-glucosides such as arbutin and salicin because of lack of expression of the bglBSRC operon, which contains structural genes for transport (bglC) and hydrolysis (bglB) of phospho-β-glucosides. Mutants carrying lesions in the cis-acting regulatory site bglR metabolize β-glucosides as a consequence of expression of this cryptic operon (Prasad and Schaefler 1974). We isolated mutations promoting β-glucoside metabolism that were unlinked to bglR; some of these mutations were shown to be amber. All of them were mapped at 27 min on the E. coli K12 linkage map and appeared to define a single gene, for which we propose the designation bglY. Utilization of β-glucosides in bglY mutants appeared to be a consequence of expression of the bglBSRC operon, since bglB bglR and bglB bglY double mutants had the same phenotype. All bglY mutations analyzed were recessive to the wild-type bglY  + allele. Phospho-β-glucosidase B and β-glucoside transport activities are inducible in bglY mutants, as they are in bglR mutants. Metabolism of β-glucosides in both bglR and bglY mutants required cyclic AMP. We propose that bglY encodes a protein acting as a repressor of the bglBSRC operon, active in both the presence and absence of β-glucosides, whose recognition site would be within the bglR locus.

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