Specificity and structural basis for linoleic acid modulation of the PhoP/PhoQ two component system

CARABAJAL, MA; LOBERTTI, C.; BRUNA, R.; GARCÍA VÉSCOVI, E.

Paraná, Entre Ríos

Congreso; LIV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB).; 2018

SAIB

PhoP/PhoQ is a two-component system (TCS) distributed amongst several Gram negative bacteria, consisting of the histidine kinase PhoQ, and the transcriptional regulator PhoP. The PhoP/PhoQ system regulates the adaptation to Mg2+-limiting environments, and controls virulent phenotypes in pathogenic bacteria. InS. Typhimurium, PhoP/PhoQ controls the invasion and proliferation within host cells. We have previously reported that long chain unsaturated fatty acids (LCUFAs) are input signals of theS. TyphimuriumPhoPQ TCS, repressing the transcription of PhoP regulated genes by inhibiting PhoQautokinase activity. In addition, NMR data obtained by our group pointed that LCUFAs act as ligands for PhoQ periplasmic domain (PhoQp). The aims of this work were to determine if LCUFAs repression upon PhoPQ signaling also occurs in other Enterobacteriaceae; and to identify specific PhoQp amino acid residues involved in LCUFAs-sensing. We constructed a series oflacZ- transcriptional fusions to previously characterized PhoP-activated genes inEscherichia coliandSerratia marcescens. We also performed site-directed mutagenesis overS. TyphimuriumphoQ, obtaining a number of PhoQ mutants with substitutions or deletions in PhoQp domain. β-galactosidase assays showed that there was no significant PhoP/PhoQ modulation by growth in LB medium supplemented with linoleic acid either inE. coliorS. marcescens. In addition, only two of the engineered mutant variants of PhoQp showed altered linoleic acid repression. Taken together, our results suggest that LCUFAs modulation isSalmonella-exclusive.