RENATURATION OF RHODANESE BY TRANSLATIONAL ELONGATION-FACTOR (EF) TU - PROTEIN REFOLDING BY EF-TU FLEXING

The translation elongation factor (EF) Tu has chaperone-like capacity to promote renaturation of denatured rhodanese. This renaturation acti vity is greatly increased under conditions in which the factor can osc illate between the open and closed conformations that are induced by G DP and GTP, respectively, Oscillation occurs during GTP hydrolysis and subsequent replacement of GDP by EF-Ts which is then displaced by GTP , Renaturation of rhodanese and GTP hydrolysis by EF-Tu are greatly en hanced by the guanine nucleotide exchange factor EF-Ts, However, renat uration is reduced under conditions that stabilize EF-Tu in either the open or closed conformation, Both GDP and the nonhydrolyzable analog of GTP, GMP-PCP, inhibit renaturation. Kirromycin and pulvomycin, anti biotics that specifically bind to EF-Tu and inhibit its activity in pe ptide elongation, also strongly inhibit EF-Tu-mediated renaturation of denatured rhodanese to levels near those observed for spontaneous, un assisted refolding, Kirromycin locks EF-Tu in the open conformation in the presence of either GTP or GDP, whereas pulvomycin locks the facto r in the closed conformation, The results lead to the conclusion that flexing of EF-Tu, especially as occurs between its open and closed con formations, is a major factor in its chaperone-like refolding activity .