mgtA and magnesium homeostasis in Salmonella, The role of the 5´untranslated region elements

SILVANA SPINELLI; LUCAS B. PONTEL; ELEONORA GARCÍA VÉSCOVI, ; FERNANDO C. SONCINI

Iguazú, Argentina

Congreso; Argentine Society for Biochemistry and Molecular Biology XL Annual Meeting. Protein Phosphorylation and Bioregulation Symposium; 2004

SAIB

Magnesium intracellular levels are tightly regulated within the cell because it is required for a wide variety of cellular functions. In Salmonella, three transporters mediate Mg2+ uptake: the P-type ATPases MgtA and MgtB, whose expression is induced by the PhoP/PhoQ two-component system; and the constitutively expressed ion-channel, CorA. We have previously reported a novel checkpoint in the Mg2+ deprivation response. This mechanism can detect this cellular stress bypassing PhoQ, posing an additional control over the expression of mgtA and mgtCB. In this work we demonstrate that this regulation modulates the intracellular levels of the magnesium transporters by controlling the transcription initiation step, trough a mechanism dependent of topological factors. Moreover, strains lacking the 5?UTR of mgtA did not show the PhoQ-independent regulation, suggesting that transcription attenuation could be involved in the control of magnesium homeostasis. We further characterized the 5´untranslated region elements by testing the effect of deleting distinct stem loop structures. This study provides new insights into the mechanisms that allow Salmonella to proliferate within its host.