Regulation of the general stress response sigma factor σ^T by Lon-mediated proteolysis

Regulated protein degradation is a critical process in all cell types, which contributes to the precise regulation of protein amounts in response to internal and external cues. In bacteria, protein degradation is carried out by ATP-dependent proteases. Although past work revealed detailed insights into the operation principles of these proteases, there is limited knowledge about the substrate proteins that are degraded by distinct proteases and the regulatory role of proteolysis in cellular processes. This study reveals a direct role of the conserved protease Lon in regulating σ^T, a transcriptional regulator of the general stress response in α-proteobacteria. Our work is significant as it underscores the importance of regulated proteolysis in modulating the levels of key regulatory proteins under changing conditions.