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Membrane sequestration by the EIIB domain of the mannitol permease MtlA activates the B acillus subtilis mtl operon regulator MtlR
Author(s) -
Bouraoui Houda,
Ventroux Magali,
NoirotGros MarieFrançoise,
Deutscher Josef,
Joyet Philippe
Publication year - 2013
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 - 10.1111/mmi.12131
Subject(s) - biology , operon , permease , complementation , biochemistry , pep group translocation , activator (genetics) , microbiology and biotechnology , mutant , receptor , gene
Summary In most firmicutes expression of the mannitol operon is regulated by MtlR . This transcription activator is controlled via phosphorylation of its regulatory domains by components of the phosphoenolpyruvate : carbohydrate phosphotransferase system ( PTS ). We found that activation of B acillus subtilis MtlR also requires an interaction with the EIIB Mtl domain of the mannitol permease MtlA ( EIICB Mtl ). The constitutive expression of the mtlAFD operon in an mtlF mutant was prevented when entire mtlA or only its 3′ part ( EIIB Mtl ) were deleted. Yeast two‐hybrid experiments revealed a direct interaction of the EIIB Mtl domain with the two C ‐terminal domains of MtlR . Complementation of the Δ3′‐ mtlA Δ mtlF or Δ mtlAFD mutants with mtlA restored constitutive MtlR activity, whereas complementation with only 3′‐ mtlA had no effect. Moreover, synthesis of EIIB Mtl in strains producing constitutively active MtlR caused MtlR inactivation. Interestingly, EIIB Mtl fused to the trans‐membrane protein YwqC restored constitutive MtlR activity in the above mutants. Replacing the phosphorylatable Cys with Asp in MtlA or soluble EIIB Mtl lowered MtlR activation, indicating that MtlR does not interact with phosphorylatyed EIIB Mtl . Induction of the B . subtilis mtl operon therefore follows a novel regulation mechanism where the transcription activator needs to be sequestered to the membrane by unphosphorylated EIICB Mtl in order to be functional.