Expression of the Uhp Sugar-Phosphate Transport System ofEscherichia coli

Abstract

This chapter reviews the regulation of the Uhp system, which is a sugar-phosphate transport protein whose expression is induced by external glucose 6-phosphate (Glu6P). The presence of organophosphate transport systems in many gram-positive and gram-negative bacteria suggests that their organophosphate substrates are widely available. Several organophosphate transport systems have been analyzed in Escherichia coli or Salmonella typhimurium. Expression of UhpT also occurs as part of the OxyR peroxide response system. As expected, loss of uhpA resulted in complete loss of detectable uhpT expression. The dominant negative behavior is explained if the truncated variants retain repression of uhpA but lack the ability to activate transcription of uhpT, analogous to the situation in LuxR. Linker substitution mutations in which the native sequences in the -64 region are converted to an NcoI restriction site reduced or eliminated promoter function, depending on the location of the substitution and the number of base pair residues that were changed. Several surface-exposed regions of the catabolite gene activator protein (CAP) have been found to be necessary for transcription activation at CAP-dependent promoters that do not require the action of other transcription activator proteins. Sugar phosphates that are not directly metabolized by glycolysis also inhibit growth of those cells but do not elicit cell killing or methylglyoxal production.