Globally modulates RNA abundance by binding to RNase E (Rne) and regulating its endonucleolytic activity. Can modulate Rne action in a substrate-dependent manner by altering the composition of the degradosome. Interacts with the C-terminal region of Rne. Constitutively expressed. Expression is increased by a reduction in intracellular concentration of UDP-GlcNAc. RraA and RraB interact with Rne at separate sites within the Rne and exert distinct effects on the composition of the degradosome, affecting distinct sets of RNA transcripts. Belongs to the RraB family.