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A novel regulatory role of glucose transporter of Escherichia coli : membrane sequestration of a global repressor Mlc
Author(s) -
Tanaka Yuya,
Kimata Keiko,
Aiba Hiroji
Publication year - 2000
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/19.20.5344
Subject(s) - biology , repressor , escherichia coli , transporter , membrane transport protein , escherichia coli proteins , glucose transporter , microbiology and biotechnology , biochemistry , gene , gene expression , insulin
External glucose stimulates transcription of several genes including ptsG encoding IICB Glc , a membrane component of the phosphotransferase system (PTS), by relieving the negative regulation of a global repressor Mlc in Escherichia coli . We investigate here how glucose modulates Mlc action. The Mlc‐mediated repression is eliminated by a ptsI mutation, while Mlc is constitutively active in a ptsG mutant. We show that IICB Glc ‐FLAG interacts physically with Mlc in crude extracts prepared from cells in which IICB Glc is supposed to exist as the non‐phosphorylated form. The IICB Glc –Mlc interaction is no longer observed when IICB Glc is phosphorylated. Exogenously added purified Mlc binds to purified IICB Glc ‐FLAG. We also demonstrate that Mlc is associated with membrane when IICB Glc is dephosphorylated while it is in the cytoplasm when IICB Glc is phosphorylated or absent. We conclude that IICB Glc regulates the cellular localization of Mlc, depending on its phosphorylation state, which is determined by the availability of external glucose. Thus, glucose induces the transcription of Mlc‐regulated promoters by sequestering Mlc to the membrane through dephosphorylation of IICB Glc .