Cooperación funcional entre chaperones mayoritarios de Escherichia coli K-12

EYDALLIN, G., MUSSI, M. A., MORÁN BARRIO, J., 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

It has been proposed that Trigger Factor (TF) and the DnaK system perform redundant functions in the holding of newly-synthesized polypeptides in E. coli. Accordingly, the functioning of the DnaK system would be highly compromised by mutations in the tig gene or genes encoding components of the DnaK system such as dnaJ. To test this hypothesis, we constructed double mutants of E. coli K-12 lacking DnaJ and TF (DtigDdnaJ, GE4103), and characterized them both genetically and biochemically. Contrasting the situation found in simple Dtig or DdnaJ mutants, GE4103 showed much lower duplication rates at permissive temperatures, and an upper limit of growth temperature of 37ºC. DnK and GroEL, the major heat-shock proteins of E. coli, were largely overproduced in GE4103, to levels much higher than the wild-type strain or the single mutants. This indicates a deficient functioning of DnaK as a negative regulator of the heat-shock response. Moreover, two major proteins, identified by MALDI-TOF as the outer membrane protein OmpW and the general regulator of the stationary phase Dps, were absent in GE4103. These results indicate that their expression of secretion depends on the cooperation between TF and the DnaK system.