Roles of the 5'-phosphate sensor domain in RNase E.

Viable mutations affecting the 5'-phosphate sensor of RNase E, including R169Q or T170A, become lethal when combined with deletions removing part of the non-catalytic C-terminal domain of RNase E. The phosphate sensor is required for efficient autoregulation of RNase E synthesis as RNase E R169Q is strongly overexpressed with accumulation of proteolytic fragments. In addition, mutation of the phosphate sensor stabilizes the rpsT P1 mRNA as much as sixfold and slows the maturation of 16S rRNA. In contrast, the decay of other model mRNAs and the processing of several tRNA precursors are unaffected by mutations in the phosphate sensor. Our data point to the existence of overlapping mechanisms of substrate recognition by RNase E, which lead to a hierarchy of efficiencies with which its RNA targets are attacked.