Figure 1. The bacterial degradosomes.

RNA degradosomes from different bacteria use similar mechanisms to degrade RNA. In E. coli, degradation of most RNAs begins by an endoribonucleotytic cleavage, followed by the fast removal of intermediates by 3′–5′ exoribonucleases, which may be assisted by RNA helicases to remove secondary structures, inhibitory for PNPase. The initiating endoribonucleolytic cleavage step is favoured by RppH removing the 5′ triphosphate to stimulate RNase E activity. The general mRNA degradation pathway is thought to be similar in Gram-positive bacteria, but is achieved by a different set of enzymes as for example the 5′–3′ exoribonuclease RNase J and the endoribonuclease RNase Y. These enzymes, along with the RNA helicase, have been proposed to associate into a degradosome.