Nitric oxide inhibits the cochaperone activity of the RING finger-like protein DnaJ

As a consequence of bacterial infection and the ensuing inflammation, expre ssion of the inducible NO synthase results in prolonged synthesis of NO in high concentrations, which among other functions, contributes to the innate defense against the infectious agent. Here we show that NO inhibits the ab ility of the bacterial cochaperone DnaJ containing a RING finger-like domai n to cooperate with the Hsp70 chaperone DnaK in mediating correct folding o f denatured rhodanese. This inhibition is accompanied by S-nitrosation of D naJ as well as by Zn2+ release from the protein. In contrast, NO has no eff ect on the activity of GroEL, a bacterial chaperone without zinc sulfur clu sters. Escherichia coli cells lacking the chaperone trigger factor and thus relying on the DnaJ/DnaK system are more susceptible toward NO-mediated cy tostasis than are wildtype bacteria. Our studies identify the cochaperone D naJ as a molecular target for NO. Thus, an encounter of bacterial cells wit h NO can impair the protein folding activity of the bacterial chaperone sys tem, thereby increasing bacterial susceptibility toward the defensive attac k by the host. (C) 2001 Academic Press.