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. 1976 Sep 25;251(18):5522-7.

Regulation of carbohydrate permeases and adenylate cyclase in Escherichia coli. Studies with mutant strains in which enzyme I of the phosphoenolpyruvate:sugar phosphotransferase system is thermolabile

  • PMID: 184083
Free article

Regulation of carbohydrate permeases and adenylate cyclase in Escherichia coli. Studies with mutant strains in which enzyme I of the phosphoenolpyruvate:sugar phosphotransferase system is thermolabile

L Castro et al. J Biol Chem. .
Free article

Abstract

Carbohydrate uptake and cyclic adenosine 3':5'-monophosphate (cyclic AMP) synthesis were studied employing mutant strains of Escherichia coli in which Enzyme I of the phosphoenolpyruvate:sugar phosphotransferase system was heat-labile. Partial loss of Enzyme I activity, which resulted from incubation of cells at the nonpermissive temperature, depressed the rate and extent of methyl alpha-glucoside uptake. Temperature inactivation of Enzyme I also rendered cyclic AMP synthesis and the uptake of several carbohydrates (glycerol, maltose, melibiose, and lactose) hypersensitive to inhibition by methyl alpha-glucoside. Protein synthesis did not appear to be required for these effects. The parental strains and "revertant" strains in which Enzyme I was less sensitive to temperature did not exhibit heat-enhanced regulation. Inhibition was abolished by the crr mutation. The results suggest that Enzyme I functions as a catalytic component of the regulatory system. Simple positive selection procedures are described for the isolation of bacterial mutants which are deficient for either Enzyme I or the heat-stable protein of the phosphotransferase system.

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