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The role of the trehalose system in regulating the maltose regulon of Escherichia coli
Author(s) -
Decker Katja,
Gerhardt Friederike,
Boos Winfried
Publication year - 1999
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.1365-2958.1999.01395.x
Subject(s) - derepression , maltose , regulon , biology , biochemistry , trehalose , repressor , inducer , mutant , gene , gene expression , enzyme , psychological repression
The maltose regulon consists of 10 genes encoding an ABC transporter for maltose and maltodextrins as well as enzymes necessary for their degradation. MalK, the energy‐transducing subunit of the transport system, acts phenotypically as a repressor of MalT, the transcriptional activator of the mal genes. Using MacConkey maltose indicator plates we isolated an insertion mutation that strongly reduced the repressing effect of overproduced MalK. The insertion had occurred in treR encoding the repressor of the trehalose system. The loss of TreR function led to derepression of treB encoding an enzymeII Tre of the PTS for trehalose and of treC encoding TreC, the cytoplasmic trehalose‐6‐phosphate hydrolase. Further analysis revealed that maltose can enter the cell by facilitated diffusion through enzymeII Tre , thus causing induction of the maltose system. In addition, derepression of TreC by itself caused induction of the maltose system, and a mutant lacking TreC was reduced in the uninduced level of mal gene expression indicating synthesis of endogenous inducer by TreC. Extracts containing TreC transformed [ 14 C]‐maltose into another 14 C‐labelled compound (preliminarily identified as maltose 1‐phosphate) that is likely to be an alternative inducer of the maltose system.