Study of the regulation and function of the inner membrane protein Sbma in an E. coli tolC mutant.

NATALIA CORBALáN; RICARDO DE CRISTóBAL; MóNICA A. DELGADO; PAULA A. VINCENT

Tucumçan

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología molecular.; 2009

SbmA transports MccB17, MccJ25, bleomycin and proline rich peptides into the E. coli cytoplasm. sbmA gene homologous were found in a variety of bacteria suggesting that an important physiological role might exist for these genes, which remains unknown. We studied the sbmA expression in a tolC mutant background, resulting in strong increases of â-galactosidase activity levels, indicating a sbmA positive regulation control by the absence of tolC gene. The goal of this work was determinate the mechanism of this sbmA regulation. It is know that tolC mutation is involved in the regulation of the porins, OmpC and OmpF, through MicF. Our results indicated that MicF is not involved in the sbmA regulation. sbma was also regulated in response to the temperature of the growth medium. We observed that the regulation in a tolC mutant was reverted when ompR or lrP genes were mutated. E. coli responds to the osmolarity changes by OmpR phosphorylation state regulation, which controls the porins expression levels. We analyzed the effects of the osmolarity shift on sbmA expression in different genetics backgrounds. OmpR overexpression increased the óE activity, so we tested rybB expression, a óE dependent gene, in sbmA, tolC and in sbmA-tolC double mutants to determinate if these mutations are able to enhance the óE activity. Our results suggest a possible function of SbmA in the stress responses.