The tolC locus affects the expression of sbmA through sE activity increase

NATALIA CORBALÁN; CONRADO ADLER; RICARDO DE CRISTÓBAL; MARÍA FERNANDA POMARES; MONICA DELGADO; PAULA VINCENT

FEMS MICROBIOLOGY LETTERS

WILEY-BLACKWELL PUBLISHING, INC

Año: 2010 vol. 311 p. 185 - 192

0378-1097

The SbmA protein is involved in the transport of MccB17-, MccJ25-, bleomycinand proline-rich peptides into the Escherichia coli cytoplasm. sbmA gene homologues were found in a variety of bacteria. However, the physiological role of this protein still remains unknown. Previously, we found that a combination of sbmA and tolC mutations in Tn10-carrying E. coli K-12 strains results in hypersusceptibility to tetracycline. In this work, we studied sbmA expression in a tolC mutant background and observed an increased expression throughout growth. We ruled out the global transcriptional regulator RpoS and the small RNA micF as intermediates in this regulation. The tolC mutation induced the expression of other well-characterized strong sigma E-dependent promoters in E. coli. We observed that the increase in sigma E activity led to a greater sbmA expression, conversely eliminating sigma E prevented expression of sbmA. We also observed that the sbmA upregulation in a tolC mutant context was abolished in an rpoE-null strain. These results suggest a sigma E-dependent positive regulation on sbmA by the tolC mutation. We hypothesize that this mechanism might be part of a compensatory cell envelope stress response.