LeuO antagonizes H-NS and StpA-dependent repression in Salmonella enterica ompS1.
The ompS1 gene encodes a quiescent porin in Salmonella enterica. We analysed the effects of H-NS and StpA, a paralogue of H-NS, on ompS1 expression. In an hns single mutant expression was derepressed but did not reach the maximum level. Expression in an stpA single mutant showed the same low repressed level as the wild type. In contrast, in an hns stpA background, OmpS1 became abundant in the outer membrane. The expression of ompS1 was positively regulated by LeuO, a LysR-type quiescent regulator that has been involved in pathogenesis. Upon induction of the cloned leuO gene into the wild type, ompS1 was completely derepressed and the OmpS1 porin was detected in the outer membrane. LeuO activated the P1 promoter in an OmpR-dependent manner and P2 in the absence of OmpR. LeuO bound upstream of the regulatory region of ompS1 overlapping with one nucleation site of H-NS and StpA. Our results are thus consistent with a model where H-NS binds at a nucleation site and LeuO displaces H-NS and StpA.
De la Cruz
Miguel Angel
MA
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62260 México.
Fernández-Mora
Marcos
M
Guadarrama
Carmen
C
Flores-Valdez
Mario Alberto
MA
Bustamante
Víctor H
VH
Vázquez
Alejandra
A
Calva
Edmundo
E
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015153:Blotting, Western; D018983:DNA Footprinting / Q000379:methods; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial; D008954:Models, Biological; D009154:Mutation; D018272:Porins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D019779:Salmonella enterica / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C031908:H-NS protein, bacteria; D018272:Porins; D003850:Deoxyribonuclease I