Molecular Chaperones involved in the secretion of metallo-b-lactamases in Gram-negative bacteria

MORAN BARRIO, J; LIMANSKY, A. S.;; VIALE, A. M

Iguazú, Misiones, Argentina.

Congreso; XL Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2004

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

The proper functioning of extracytoplasmatic proteins requires their export to their proper compartment. In Escherichia coli, periplasmic proteins are synthesized in the cytoplasm as precursors and directed to the general secretory pathway (Sec). Whether and how cytoplasmatic chaperones participate in their secretion is still obscure. We studied the cooperation of these chaperones with the Sec pathway in E. coli by genetic procedures using as a model system the metallo-b-lactamase GOB from Chryseobacterium meningosepticum. We developed a functional procedure to analyze the proper expression and secretion of GOB in E. coli chaperone mutants, consisting in determining b-lactam resistance by a plate dilution assay. We demonstrated that SecA and SecY play fundamental roles in proper GOB secretion. Cytoplasmic chaperones including DnaK, DnaJ and Trigger Factor (TF) were also necessary for this process. The use of double mutants provided further evidence for a cooperation between TF and SecA in GOB secretion. These overall data further highlight the existence of complex interactions between cytoplasmic chaperones and the Sec machinery in the secretion of pathogenicity factors such as metallo-b-lactamases in Gram-negative bacteria.