Study of the regulation and function of the inner membrane protein Sbma

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

Carlos Paz, Córdoba

Congreso; XLIV Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología molecular; 2008

The SbmA protein transports MccB17, MccJ25, bleomycin and proline rich peptides into the Escherichia coli. Homologs of the sbmA gene are found in a variety of bacteria suggesting an important physiological role might exist for these genes, however it remain unknown. In this work we described the study of the sbmA regulation in Escherichia coli and Salmonella typhimurium. Using the chromosomal transcriptional lacZ fusion in the sbmA gene of these two gram-negative bacterial, we demonstrated that sbmA expression is regulated by the PhoP/PhoQ two-component system. Previously, we demonstrated that the double mutant sbmA tolC shows a Tc hypersensitivity phenotype, so we studied the sbmA::lacZ expression in a tolC mutant. We observed high level of â-galactosidase activity in this genetic background, indicating a positive regulation by tolC mutation. We tested the expression of sbmA::lacZ in E. coli tolC mutant growing in minimal medium with low Mg2+ concentration to determine a hypothetical additive effect of two regulation mechanisms. Interestingly, we observed that there is a relationship between tolC mutant effect and the PhoP/PhoQ-dependent activation. Moreover we observed a deficient growth phenotype of sbmA mutant in medium containing low magnesium. The future understanding of sbmA regulation mechanism would let to hypostatize a physiological function for this membrane protein.