INVESTIGADORES
DELPINO Maria Victoria
congresos y reuniones científicas
Título:
Funtional characterization of ABC-MFP Membrane Transport System and TolC Homologue in Brucella suis.
Autor/es:
FERNANDO MARTÍN; DIANA POSADAS; M. VICTORIA DELPINO; PABLO C. BALDI; ELEONORA CAMPOS; ANGELES ZORREGUIETA
Lugar:
Estados Unidos
Reunión:
Congreso; 105 th General Meeting of the ASM.; 2005
Resumen:
Abstract Gram-negative bacteria have envolved transport complexs that export macromolecules and toxic substances across both inner and outer membranes in a single energy coupled step. The process requires a cytoplasmatic membrane export system (ABC or RND), an accesory protein (MFP), and an outer membrane factor (OMF) of the TolC family. The roles of these systems in Brucella spp. remain unexplored. Brucella is a Gram-negative intracellular pathogen able to replicate and survive inside phagocytic and non phagocytic cells. Therefore, protein secretion and efflux of toxic compounds may be crucial in the infection process. Two ABC-MFP putative system and only one protein of the TolC family have been identified in the B. suis genome. Phylogenetic analysis of the MFP components placed them close to those involved in drug efflux. Both loci encoding for the ABC-MFP systems and tolCb gene were cloned under the inducible ara promoter. Complementation studies on heterologous mutants affected in protein secretion or drug effux were performed. Protein secretion was assayed by different plate assays and SDS-PAGE. Drug efflux was analyzed by measuring the minimun inhibitory concentration (MIC) of different compounds such as detergents, drugs and antibiotics. The cloned ABC-MFP systems were unable to complement the secretion phenotype of the R leguminosarum prsD-prsE mutant, which encodes for an ABC-MFP protein secretion system. However, one of these systems restored resistance to nalidixic acid and rhodamine 6-G in the acrAB hypersensitive mutant of E. coli. No evidence for complementation of the resistence hemolysin secretion was observed. A mutant in a tolC homologue has been isolated in Rhizobium . Interestingly, this mutant showed a defect in growth that was restored by tolCbof Brucella. These results suggest that in B. suis at least one of the ABC-MFP systems may be involved in efflux of toxic compounds. In addition, proteins of the TolC family may play in Rhizobiaceae some other physiological role that has noy yet been described.