Fig. 4: The bridging element in the TEC-IC complex is accessible to the RNA degradosome.

A Schematic of the ompD transcript and MicC recognition site. B, C Cleavage time courses of ompD mRNA fragment and +83-cleavage intermediate species (see Fig. 2D and Suppl. Fig. 8 for representative raw data). Free ompD mRNA fragment (black), ompD₈₉-TEC (green), ompD₈₉-30S IC (grey) and ompD₈₉-TEC-IC (red) were incubated with MicC/Hfq and then subjected to cleavage by the RNA degradosome. Reactions were stopped at indicated time points and analysed by denaturing PAGE. Data are mean ± SD from three independent reactions. Degradation trajectories of ompD were fitted to one phase exponential decay. Formation and decay of intermediates from ompD-cleavage at position +83 were fitted to two-exponential equation [I = exp(-kt) – exp(-jt)] with degradation rate k and formation rate j. D Cleavage specificities for nucleolytic processing of site +83 in ompD in the different assembly states, expressed as the formation rate of the +83 intermediate over the degradation rate of the respective ompD fragment starting material. Data are mean ± SD from three independent reactions. E Conformational substates of the TEC-30S IC assembly. F Substate of the early expressome proposed to facilitate the accommodation of Hfq/MicC on the bound ompD mRNA. The colours of the segmented map in (E) correspond to the components shown in the schematic.