Premium
Inducer exclusion by glucose 6‐phosphate in Escherichia coli
Author(s) -
Hogema Boris M.,
Arents Jos C.,
Bader Rechien,
Eijkemans Kevin,
Inada Toshifumi,
Aiba Hiroji,
Postma Pieter W.
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.00833.x
Subject(s) - catabolite repression , dephosphorylation , biochemistry , inducer , biology , enzyme , enzyme repression , enzyme inducer , lactose , mutant , escherichia coli , psychological repression , phosphatase , gene expression , gene
The main mechanism causing catabolite repression by glucose and other carbon sources transported by the phosphotransferase system (PTS) in Escherichia coli involves dephosphorylation of enzyme IIA Glc as a result of transport and phosphorylation of PTS carbohydrates. Dephosphorylation of enzyme IIA Glc leads to ‘inducer exclusion’: inhibition of transport of a number of non‐PTS carbon sources (e.g. lactose, glycerol), and reduced adenylate cyclase activity. In this paper, we show that the non‐PTS carbon source glucose 6‐phosphate can also cause inducer exclusion. Glucose 6‐phosphate was shown to cause inhibition of transport of lactose and the non‐metabolizable lactose analogue methyl‐β‐ D ‐thiogalactoside (TMG). Inhibition was absent in mutants that lacked enzyme IIA Glc or were insensitive to inducer exclusion because enzyme IIA Glc could not bind to the lactose carrier. Furthermore, we showed that glucose 6‐phosphate caused dephosphorylation of enzyme IIA Glc . In a mutant insensitive to enzyme IIA Glc ‐mediated inducer exclusion, catabolite repression by glucose 6‐phosphate in lactose‐induced cells was much weaker than that in the wild‐type strain, showing that inducer exclusion is the most important mechanism contributing to catabolite repression in lactose‐induced cells. We discuss an expanded model of enzyme IIA Glc ‐mediated catabolite repression which embodies repression by non‐ PTS carbon sources.