degradosome

The degradosome is a multi-enzyme ribonucleolytic complex in bacteria that coordinates RNA decay and processing in the cytoplasm. It serves to accelerate and regulate the turnover of messenger RNA and other RNA species, helping the cell respond to changing conditions and maintain RNA quality control.

In Escherichia coli and many Gram-negative bacteria, the degradosome centers on the endoribonuclease RNase E, which acts as a scaffold to recruit core components. The typical core includes the 3' to 5' exoribonuclease PNPase, the DEAD-box RNA helicase RhlB, and the glycolytic enzyme enolase. RNase E cleaves target RNAs to create entry points for degradation, while PNPase degrades RNA from the 3' end and RhlB helps unwind structured regions to enable access. Enolase associates with the complex, though its exact role in RNA decay is not fully understood and may relate to coordinating metabolism with RNA processing.

Localization and dynamics are notable features: in E. coli the degradosome is associated with the inner cytoplasmic membrane via a membrane-targeting sequence in RNase E, and its composition can vary with growth conditions and stress. Variants exist in other bacteria, where different RNases can serve as structural anchors for degradosome-like assemblies. These complexes are central to rapid mRNA turnover, riboregulator regulation, and cellular responses to environmental cues, reflecting a conserved strategy for efficient RNA management across bacteria.