INCREASED SYNTHESIS OF DNAK, GROEL, AND GROES HOMOLOGS BY FRANCISELLA-TULARENSIS LVS IN RESPONSE TO HEAT AND HYDROGEN-PEROXIDE

The response of the facultative intracellular bacterium Francisella tu larensis LVS to stress was assayed by pulse-labeling with [S-35]methio nine followed by two-dimensional gel electrophoresis and autoradiograp hy. A temperature increase from 37 to 42 degrees C or exposure to 5 mM hydrogen peroxide induced increased syntheses of at least 15 proteins . Among these proteins were a 75-, a 60-, and a 10-kDa protein. By N-t erminal sequence analysis, these three proteins were found to be exten sively homologous to the highly conserved chaperone proteins DnaK, Gro EL, and GroES of Escherichia coil. Antibodies specific to the DnaK hom olog of E. coil reacted with the 75-kDa protein, and antibodies to the GroEL homolog of Legionella micdadei reacted with the 60-kDa protein. A readiness to respond to hydrogen peroxide with synthesis of the cha perone components may be fundamental to the intracellular survival of pathogens such as F. tularensis, which are exposed to oxidative stress while invading the host macrophages.