Figure 6.

Cartoon Schematic of the Guide RNA Activation of RNase E and a Potential Proofreading Mechanism

sRNA (red) is maintained in the cell in 5′PPP form. Such sRNA probably can associate with Hfq (purple) and basepair with a target mRNA (green), however 5′PPP group cannot actively stimulate RNase E (brown) (right panel). Under particular conditions (yellow lightening) the pyrophosphate from sRNA 5′ end is removed and such ‘activated’ sRNA (5′P marked with a star) efficiently guides RNase E cleavage of target mRNA (middle panel). 5′P form of sRNA would be rapidly degraded when there is no or no more target it can basepair with what would ensure ‘proofreading’ mechanism in sRNA mediated mRNA degradation.