@entity2491 has three distinct @entity1025 transport systems, the constitutive high-capacity CorA transporter and two P-type ATPases, MgtA and MgtB, whose transcription is repressed by normal concentrations of @entity1025 in the growth medium. The latter @entity1025 -transporting ATPase is part of a two-gene operon, mgtCB, with mgtC encoding a 23 kDa protein of unknown function. Transcriptional regulation using fusions of the promoter regions of mgtA and mgtCB to luxAB showed a biphasic time and @entity1025 concentration dependence. Between 1 and 6 h after transfer to @entity1568 minimal medium containing defined concentrations of @entity1025 , transcription increased about 200-fold for mgtCB and up to 400-fold for mgtA, each with a half-maximal dependence on @entity1025 of 0.5 mM. Continued incubation revealed a second phase of increased transcription, up to 2000-fold for mgtCB and up to 10,000-fold for mgtA. This secondary increase occurred between 6 and 9 h after transfer to defined medium for mgtCB but between 12 and 24 h for mgtA and had a distinct half-maximal dependence for @entity1025 of 0.01 mM. A concomitant increase of at least 1000-fold in uptake of cation was seen between 8 and 24 h incubation with either system, showing that the transcriptional increase was followed by functional incorporation of large amounts of the newly synthesized transporter into the membrane. Regulation of transcription by @entity1025 was not dependent on a functional stationary-phase sigma factor encoded by rpoS, but it was dependent on the presence of a functional phoPQ two-component regulatory system. Whereas mgtCB was completely dependent on regulation via phoPQ, the secondary late @entity1025 -dependent phase of mgtA transcription was still evident in strains carrying a mutation in either phoP or phoQ, albeit substantially diminished. Several divalent cations blocked the early phase of the increase in transcription elicited by the decrease in @entity1025 concentration, including cations that inhibit @entity1025 uptake ( @entity515 , @entity3411 and @entity3281 ) and those which do not ( @entity141 and @entity8862 ). In contrast, the second later phase of the transcriptional increase was not well blocked by any cation except those which inhibit uptake. Overall, the data suggest that at least two distinct mechanisms for transcriptional regulation of the mgtA and mgtCB loci exist.

Magnesium transport in XXXX : biphasic magnesium and time dependence of the transcription of the mgtA and mgtCB loci.

@entity2491 :: ('90371', 'Species') :: ['Salmonella typhimurium'] @entity8862 :: ('CHEBI:37256', 'Chemical') :: ['Zn2+'] @entity1568 :: ('MESH:D009584', 'Chemical') :: ['nitrogen'] @entity1025 :: ('CHEBI:18420', 'Chemical') :: ['Mg(2+)', 'Mg2+'] @entity3281 :: ('CHEBI:29035', 'Chemical') :: ['Mn2+'] @entity515 :: ('CHEBI:29334', 'Chemical') :: ['Co2+'] @entity3411 :: ('CHEBI:49786', 'Chemical') :: ['Ni2+'] @entity141 :: ('CHEBI:29108', 'Chemical') :: ['Ca2+']
@entity2491 :: (90371,Species) :: ['Salmonella typhimurium']
